Pointer detection apparatus and pointer detection method

CROSS-REFERENCE(S) TO RELATED APPLICATION(S)

p-0002The present application claims priority under 35 U.S.C. §119 from Japanese Patent Application JP 2009-145879 filed in the Japanese Patent Office on Jun. 18, 2009, the entire content of which is incorporated herein by reference.

BACKGROUND

p-00031. Field of the Invention

p-0004This invention relates to a pointer detection apparatus and a pointer detection method, and more particularly to a pointer detection apparatus and a pointer detection method wherein the position of a pointer is detected by an electrostatic coupling system.

p-00052. Description of the Related Art

p-0006Conventionally, for the detection of the position of a pointer such as a finger or a pen for use with a touch panel or a like apparatus, various systems have been proposed such as, for example, a resistive film system, an electrostatic coupling system, and an electrostatic capacity system. In recent years, a pointer detection apparatus including the electrostatic coupling system, from among the various systems mentioned above, has been vigorously developed.

p-0007Electrostatic coupling systems are roughly divided into two types including a surface capacitive type and a projected capacitive type. An electrostatic coupling system of the surface capacitive type is applied, for example, in an ATM (Automated Teller Machine), and that of the projected capacitive type is applied, for example, in a portable telephone set. It is to be noted that, in both types, a variation of the electrostatic coupling state between a conductive film and a pointer such as a finger or an electrostatic pen is detected to detect the position of the pointer.

p-0008A pointer detection apparatus of the projected capacitive type electrostatic coupling system includes an electrode formed in a predetermined pattern, for example, on a transparent substrate or a transparent film and detects a variation of the electrostatic coupling state between a pointer and the electrode when the pointer approaches the electrode. For a pointer detection apparatus of the type described, various techniques for optimizing the configuration have been proposed and are disclosed, for example, in Japanese Patent Laid-Open Nos. HEI 5-224818, HEI 6-4213, HEI 7-141088, HEI 8-87369, HEI 8-179871, HEI 8-190453, HEI 8-241161, HEI 9-45184, 2000-76014, 2000-105645, 2000-112642, and HEI 10-161795.

p-0009Here, operation of a pointer detection apparatus of the cross point type electrostatic coupling system developed from the projected capacitive type electrostatic coupling system is described briefly with reference to the accompanying drawings. <figref idrefs="DRAWINGS">FIGS. 62A and 62B</figref> illustrate a general configuration of a sensor section and a position detection principle of a pointer detection apparatus of the cross point type electrostatic coupling system.

p-0010Referring to <figref idrefs="DRAWINGS">FIGS. 62A and 62B</figref>, a sensor section <b>300</b> includes a transmission conductor group <b>303</b> formed from a plurality of transmission conductors <b>304</b>, and a reception conductor group <b>301</b> formed from a plurality of reception conductors <b>302</b>. An insulating film is formed between the transmission conductor group <b>303</b> and the reception conductor group <b>301</b>. The transmission conductors <b>304</b> extend in a predetermined direction indicated by an arrow mark X and are disposed in parallel to each other and in a spaced relationship by a predetermined distance from each other. The reception conductors <b>302</b> are in the form of a wire extending in a direction crossing the extension direction of the transmission conductors <b>304</b>, that is, in the direction indicated by an arrow mark Y in <figref idrefs="DRAWINGS">FIG. 62A</figref> and are disposed in parallel to each other and in a spaced relationship at a predetermined distance from each other.

p-0011In the sensor section <b>300</b> having the configuration described above, a predetermined signal is supplied to a predetermined one of the transmission conductors <b>304</b> and a variation of current flowing to a cross point between the predetermined transmission conductors <b>304</b> and a reception conductor <b>302</b> is detected at each of the cross points of the predetermined transmission conductors <b>304</b> and the reception conductors <b>302</b>. A system of detection just described is generally called cross point type electrostatic coupling system. At a position of the sensor section <b>300</b> at which a pointer <b>310</b> such as a finger is placed, current is shunted through the pointer <b>310</b> and varies. Therefore, the position of the pointer <b>310</b> can be detected by detecting a cross point at which current exhibits a variation. Further, in a pointer detection apparatus of the cross point type electrostatic coupling system, multipoint detection is possible because a plurality of cross points are provided on the sensor section <b>300</b> as seen in <figref idrefs="DRAWINGS">FIGS. 62A and 62B</figref>.

p-0012A principle of position detection of the cross point type electrostatic coupling system will now be described more particularly. Assume for example that a predetermined signal is supplied to the transmission conductor Y<b>6</b> and a pointing position of the pointer <b>310</b> on the transmission conductor Y<b>6</b> is detected as seen in <figref idrefs="DRAWINGS">FIG. 62A</figref>. When a signal is supplied to the transmission conductor Y<b>6</b>, the difference between currents flowing to the reception conductors X₀and X₁is detected through a differential amplifier <b>305</b>. Then, after a predetermined interval of time, the reception conductors to be used for current difference detection are changed over from the reception conductors X₀and X₁to the reception conductors X₁and X₂, and the current difference between the reception conductors X₁and X₂is detected. This operation is repeated up to the reception conductor X_M.

p-0013Thereupon, a level variation of an output signal of the differential amplifier <b>305</b> at the position of each cross point on the transmission conductor Y₆is determined <figref idrefs="DRAWINGS">FIG. 62B</figref> illustrates a characteristic of the level variation. In <figref idrefs="DRAWINGS">FIG. 62B</figref>, the axis of abscissa indicates the distance from the reception conductor X₀to each reception conductor, that is, the position of each reception conductor, and the axis of ordinate indicates the level of an output signal of the differential amplifier <b>305</b>, that is, an output value of the differential amplifier <b>305</b>. In <figref idrefs="DRAWINGS">FIG. 62B</figref>, a broken line curve represents a characteristic of the level variation of the output signal of the differential amplifier <b>305</b> and a solid line curve represents a characteristic of the integration value of the output signal of the differential amplifier <b>305</b>.

p-0014In the example illustrated in <figref idrefs="DRAWINGS">FIGS. 62A and 62B</figref>, since the pointer <b>310</b> is placed in proximity to cross points of the reception conductors X₄and X_M-5on the transmission conductor Y₆, current flowing in proximity to the cross points varies. Therefore, in the example illustrated in <figref idrefs="DRAWINGS">FIG. 62B</figref>, the output signal of the differential amplifier <b>305</b> varies at corresponding positions in proximity to the cross points of the reception conductors X₄and X_M-5on the transmission conductor Y₆, and the integration value of the output signal exhibits a low value, that is, a negative value. The position of the pointer <b>310</b> can be detected based on the variation of the integration value. In the conventional pointer detection apparatus, the detection described above is carried out while successively changing over between the transmission conductors, to be used for the detection, one by one.

SUMMARY

p-0015This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

p-0016Since such a pointer detection apparatus of the cross point type electrostatic coupling system as described above carries out a position detection process of cross points one by one per every predetermined period of time, a long period of time is required for detection at all cross points. For example, if the sensor section includes 64 transmission conductors and 128 reception conductors and the detection processing time at each of the cross points is, for example, 256 msec, then a period of time of approximately 2 seconds is required for detection at all cross points, that is, at 8,192 cross points in total. Therefore, the pointer detection apparatus as described above is not suitable for practical use.

p-0017Therefore, it is an object of the present invention to provide a pointer detection apparatus and a pointer detection method by which detection of the position of a pointer by an electrostatic coupling system can be carried out at a higher speed.

p-0018To that end, a pointer detection apparatus is described that includes a conductor pattern with a plurality of conductors disposed in a first direction and a plurality of conductors disposed in a second direction which crosses the first direction. The apparatus further includes a multi-frequency signal production circuit configured to produce a plurality of signals of different frequencies, and a first conductor selection circuit configured to selectively supply said signals of different frequencies produced by the multi-frequency signal production circuit to those first conductors, between which N number of the first conductors are interposed, N being a predetermined integer equal to or greater than 0. The apparatus still further includes a second conductor selection circuit configured to selectively receive detection signals from the plurality of second conductors, and a signal detection circuit configured to detect signals of individual frequencies, corresponding to the signals of different frequencies produced by the multi-frequency signal production circuit, which are representative of coupling states at cross points between the first conductors and the second conductors and are received from said second conductor selection circuit.

p-0019According to another aspect of the present invention, a pointer detection method is described that includes: a first step of producing a plurality of signals of different frequencies; and a second step of selectively supplying the signals of different frequencies to a conductor pattern including a plurality of first conductors disposed in a first direction and a plurality of second conductors disposed in a second direction crossing the first direction. Specifically, the second step selectively supplies the signals of different frequencies to those first conductors, between which N number of the first conductors are interposed, N being a predetermined integer equal to or greater than 0. The method further includes a third step of selectively switching those second conductors from which detection signals are to be received; and a fourth step of obtaining signals of individual frequencies, corresponding to the signals of different frequencies produced at the first step, based on the detection signals supplied from the second conductors selected at the third step. The obtained signals of individual frequencies are representative of coupling states at cross points between the first conductors and the second conductors.

p-0020In the pointer detection apparatus and the pointer detection method, a plurality of signals having frequencies different from each other are supplied at the same time to the plurality of conductors on the transmission side. Meanwhile, on the reception side, signals of individual frequencies corresponding to the plurality of signals having different frequencies are detected to determine the position of a pointer on the conductor pattern. In other words, signal processing is executed in parallel between (among) the conductors on both of the transmission side and the reception side.

p-0021A plurality of signals of different frequencies are supplied at the same time to the plurality of conductors on the transmission side to detect the position of a pointer on the conductor pattern. In other words, the position detection process can be carried out at the same time for a plurality of cross points. Therefore, the present invention makes it possible for a pointer detection apparatus of the electrostatic coupling system to carry out position detection of a pointer at a higher speed.

p-0022Furthermore, the present invention makes it possible for a pointer detection apparatus of the electrostatic coupling system to carry out position detection of multiple positions (i.e., multiple positions of multiple pointers, or of multiple fingers of one or more users) at the same time.

p-0023The above and other objects, features, and advantages of the present invention will become apparent from the following description and the appended claims, taken in conjunction with the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

p-0024The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

p-0025<figref idrefs="DRAWINGS">FIG. 1</figref> is a schematic block diagram of a pointer detection apparatus according to a first embodiment of the present invention;

p-0026<figref idrefs="DRAWINGS">FIG. 2</figref> is a schematic sectional view of a sensor section of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0027<figref idrefs="DRAWINGS">FIG. 3</figref> is a block diagram of a multi-frequency signal supplying circuit of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0028<figref idrefs="DRAWINGS">FIG. 4</figref> is a block diagram of a periodic signal production section of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0029<figref idrefs="DRAWINGS">FIG. 5</figref> is a diagrammatic view of a transmission conductor selection circuit of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0030<figref idrefs="DRAWINGS">FIG. 6</figref> is a diagrammatic view illustrating switching operation of transmission conductors in the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0031<figref idrefs="DRAWINGS">FIG. 7</figref> is a diagrammatic view of a reception conductor selection circuit and an amplification circuit of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0032<figref idrefs="DRAWINGS">FIG. 8</figref> is a diagrammatic view illustrating switching operation of reception conductors in the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0033<figref idrefs="DRAWINGS">FIG. 9</figref> is a block diagram of a reception section of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0034<figref idrefs="DRAWINGS">FIG. 10</figref> is a block diagram of a synchronous detection circuit section of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0035<figref idrefs="DRAWINGS">FIG. 11A</figref> is a schematic view illustrating an electrostatic coupling state between a transmission conductor and a reception conductor where no pointer exists on the sensor section shown in <figref idrefs="DRAWINGS">FIG. 2</figref>, and <figref idrefs="DRAWINGS">FIG. 11B</figref> is a similar view but illustrating another electrostatic coupling state between the transmission conductor and the reception conductor where a pointer exists on the sensor section shown in <figref idrefs="DRAWINGS">FIG. 2</figref>;

p-0036<figref idrefs="DRAWINGS">FIG. 12A</figref> is a schematic view illustrating a multi-touch state of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>, and <figref idrefs="DRAWINGS">FIGS. 12B</figref>, <b>12</b>C and <b>12</b>D are waveform diagrams respectively illustrating a waveform of output signals of the reception conductors on a transmission conductor, another detection waveform of output signals of the reception conductors on another transmission conductor, and a further detection waveform of output signals of the reception conductors on a further transmission conductor;

p-0037<figref idrefs="DRAWINGS">FIG. 13</figref> is a flow chart illustrating a procedure for position detection by the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0038<figref idrefs="DRAWINGS">FIG. 14</figref> is a schematic sectional view of the sensor section according to modification 1 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0039<figref idrefs="DRAWINGS">FIG. 15A</figref> is a schematic sectional view of the sensor section according to modification 2 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>, and <figref idrefs="DRAWINGS">FIG. 15B</figref> is a perspective view of the sensor section shown in <figref idrefs="DRAWINGS">FIG. 15A</figref>;

p-0040<figref idrefs="DRAWINGS">FIG. 16A</figref> is a schematic enlarged view of a cross point of the sensor section of a first example according to modification 3 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>, and <figref idrefs="DRAWINGS">FIG. 16B</figref> is a schematic further enlarged view of a land conductor portion of the sensor section shown in <figref idrefs="DRAWINGS">FIG. 16A</figref>;

p-0041<figref idrefs="DRAWINGS">FIG. 17</figref> is a schematic enlarged view of the sensor section of a second example according to modification 3 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0042<figref idrefs="DRAWINGS">FIG. 18</figref> is a schematic view showing a configuration of the sensor section according to modification 4 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0043<figref idrefs="DRAWINGS">FIG. 19A</figref> is a schematic view showing an upper conductor pattern of the sensor section shown in <figref idrefs="DRAWINGS">FIG. 18</figref>, and <figref idrefs="DRAWINGS">FIG. 19B</figref> is a schematic view showing a lower conductor pattern of the sensor section shown in <figref idrefs="DRAWINGS">FIG. 18</figref>;

p-0044<figref idrefs="DRAWINGS">FIG. 20</figref> is a schematic view showing a configuration of the sensor section according to modification 5 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0045<figref idrefs="DRAWINGS">FIG. 21A</figref> is a schematic circuit diagram of an amplifier according to modification 6 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>, and <figref idrefs="DRAWINGS">FIG. 21B</figref> is a block diagram of the amplification circuit where a differential amplifier is used and associated elements of the amplification circuit;

p-0046<figref idrefs="DRAWINGS">FIG. 22</figref> is a schematic circuit diagram of the amplifier according to modification 7 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0047<figref idrefs="DRAWINGS">FIG. 23</figref> is a schematic circuit diagram illustrating a supplying form of periodic signals according to modification 8 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0048<figref idrefs="DRAWINGS">FIG. 24</figref> is a similar view but illustrating a supplying form of periodic signals and a detection form of an output signal according to modification 9 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0049<figref idrefs="DRAWINGS">FIGS. 25A and 25B</figref> are diagrammatic views illustrating an example of rotation of the frequencies of periodic signals according to modification 9 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0050<figref idrefs="DRAWINGS">FIGS. 26A to 26C</figref> are diagrammatic views illustrating another example of rotation of the frequencies of periodic signals according to modification 9 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0051<figref idrefs="DRAWINGS">FIG. 27</figref> is a diagrammatic view illustrating a level curve detected in modification 9 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0052<figref idrefs="DRAWINGS">FIG. 28</figref> is a similar view but illustrating an example of a supplying form of periodic signals and a detection form of an output signal according to modification 10 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0053<figref idrefs="DRAWINGS">FIG. 29</figref> is a diagrammatic view showing another example of a supplying form of periodic signals and a detection form of the output signal according to modification 10 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0054<figref idrefs="DRAWINGS">FIG. 30</figref> is a diagrammatic view showing an example of a supplying form of periodic signals and a detection form of an output signal according to modification 11 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0055<figref idrefs="DRAWINGS">FIG. 31</figref> is a similar view but showing another example of a supplying form of periodic signals and a detection form of an output signal according to modification 11 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0056<figref idrefs="DRAWINGS">FIG. 32</figref> is a similar view but showing a further example of a supplying form of periodic signals and a detection form of an output signal according to modification 11 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0057<figref idrefs="DRAWINGS">FIGS. 33A and 33B</figref> are diagrammatic views showing different examples of a supplying form of periodic signals and a detection form of an output signal according to modification 12 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0058<figref idrefs="DRAWINGS">FIG. 34</figref> is a schematic diagrammatic view illustrating a signal level upon normal detection of a finger;

p-0059<figref idrefs="DRAWINGS">FIG. 35</figref> is similar view but illustrating an example of a level curve after a nonlinear process for the signal of the signal level of <figref idrefs="DRAWINGS">FIG. 34</figref>, according to modification 13 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0060<figref idrefs="DRAWINGS">FIG. 36</figref> is a diagrammatic view illustrating an example of normalized levels of output signals detected by the reception section according to modification 14 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0061<figref idrefs="DRAWINGS">FIGS. 37 and 38</figref> are diagrammatic views illustrating examples of a supplying form of periodic signals and a detection form of an output signal according to modification 15 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0062<figref idrefs="DRAWINGS">FIG. 39</figref> is a diagrammatic view showing a supplying form of periodic signals and a detection form of an output signal and illustrating a problem to be solved by modification 17 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0063<figref idrefs="DRAWINGS">FIG. 40</figref> is a similar view but showing an example of a supplying form of periodic signals and a detection form of the output signal according to modification 17 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0064<figref idrefs="DRAWINGS">FIG. 41</figref> is a block diagram of the reception section of the pointer detection apparatus according to modification 18 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0065<figref idrefs="DRAWINGS">FIG. 42</figref> is a block diagram of an absolute value detection circuit of the pointer detection apparatus according to modification 18 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0066<figref idrefs="DRAWINGS">FIG. 43A</figref> is a diagrammatic view illustrating a supplying state of periodic signals upon one-sided transmission and <figref idrefs="DRAWINGS">FIG. 43B</figref> is a diagrammatic view illustrating the level of output signals;

p-0067<figref idrefs="DRAWINGS">FIG. 44A</figref> is a diagrammatic view illustrating a supplying form of periodic signals upon double-sided transmission according to modification 19 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref> and <figref idrefs="DRAWINGS">FIG. 44B</figref> is a diagrammatic view illustrating the level of output signals;

p-0068<figref idrefs="DRAWINGS">FIG. 45A</figref> is a schematic view illustrating an example or a spatial distribution or level curved face of output signals and <figref idrefs="DRAWINGS">FIG. 45B</figref> is a view illustrating division of the level curved face into a plurality of planes according to modification 19;

p-0069<figref idrefs="DRAWINGS">FIG. 46</figref> is a graph illustrating an example of a method of calculating the volume of a level curved face according to modification 20 to the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 1</figref>;

p-0070<figref idrefs="DRAWINGS">FIG. 47</figref> is a schematic block diagram of a pointer detection apparatus according to a second embodiment of the present invention;

p-0071<figref idrefs="DRAWINGS">FIG. 48</figref> is a schematic view of a transmission conductor selection circuit and a transmission conductor connection pattern changeover circuit of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 47</figref>;

p-0072<figref idrefs="DRAWINGS">FIGS. 49A and 49B</figref> are diagrammatic views illustrating switching operation of transmission conductors of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 47</figref>;

p-0073<figref idrefs="DRAWINGS">FIG. 50</figref> is a diagrammatic view of a reception conductor selection circuit and a reception conductor connection pattern changeover circuit of the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 47</figref>;

p-0074<figref idrefs="DRAWINGS">FIG. 51</figref> is a diagrammatic view illustrating switching operation of reception conductors by the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 47</figref>;

p-0075<figref idrefs="DRAWINGS">FIGS. 52A and 52B</figref> are diagrammatic views illustrating an example of switching operation of transmission conductors by a pointer detection apparatus according to a third embodiment of the present invention;

p-0076<figref idrefs="DRAWINGS">FIGS. 53A and 53B</figref> are diagrammatic views illustrating another example of switching operation of transmission conductors by the pointer detection apparatus according to the second embodiment of the present invention;

p-0077<figref idrefs="DRAWINGS">FIG. 54</figref> is a schematic block diagram of a pointer detection apparatus according to a fourth embodiment of the present invention;

p-0078<figref idrefs="DRAWINGS">FIG. 55</figref> is a waveform diagram illustrating an example of dispersion of initial phases of periodic signals;

p-0079<figref idrefs="DRAWINGS">FIG. 56</figref> is a graph illustrating a composite waveform of transmission signals by the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 54</figref> where no phase dispersion is applied;

p-0080<figref idrefs="DRAWINGS">FIGS. 57 to 61</figref> are graphs illustrating composite waveforms of transmission signals by the pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 54</figref> where different patterns of phase dispersion are applied; and

p-0081<figref idrefs="DRAWINGS">FIG. 62A</figref> is a schematic view of a sensor section of a conventional pointer detection apparatus of the cross point type electrostatic coupling system, and <figref idrefs="DRAWINGS">FIG. 62B</figref> is a view illustrating a principle of position detection by the conventional cross point type pointer detection apparatus of <figref idrefs="DRAWINGS">FIG. 62A</figref>.

DETAILED DESCRIPTION

p-0082Several embodiments of the present invention will be described with reference to the accompanying drawings. One skilled in the art will appreciate that the present invention is not limited to the described embodiments; the descriptions are provided for illustrative purposes only. The description is given in the following order.

p-00831. First Embodiment (example of scanning within a group in the frequency multiplexing system);

p-00842. Second Embodiment (example of scanning while switching between block units in the frequency multiplexing system);

p-00853. Third Embodiment (example of scanning of all conductors in the frequency multiplexing system); and

p-00864. Fourth Embodiment (example wherein initial phases of multi-frequency signals are dispersed in the frequency multiplexing system).

1. First Embodiment

p-0087A first embodiment of the present invention relates to a basic configuration of a pointer detection apparatus and a pointer detection method of the present invention.

p-0088In the present embodiment, each of a transmission conductor group and a reception conductor group of a sensor section is divided into a plurality of groups, and signals in the form of periodic signals having frequencies different from each other among the different groups are supplied simultaneously, that is, multiplex transmitted. In the following description, the supplying form of signals in the present embodiment is referred to as “frequency multiplex system” or “frequency multiplex type,” and a plurality of periodic signals supplied are generally referred to as “multi-frequency signal.” The position detection system in the present invention is an electrostatic coupling system wherein the position of a pointer is detected based on a variation of the electrostatic coupling state between a transmission conductor and a reception conductor of the sensor section.

p-0089[Configuration of the Pointer (i.e., Position Indicator) Detection Apparatus]

p-0090<figref idrefs="DRAWINGS">FIG. 1</figref> shows a general configuration of the pointer detection apparatus according to the first embodiment of the present invention.

p-0091Referring to <figref idrefs="DRAWINGS">FIG. 1</figref>, a pointer detection apparatus <b>100</b> shown includes, as principal components thereof, a sensor section <b>10</b>, a transmission section <b>20</b>, a reception section <b>30</b>, and a control circuit <b>40</b> for controlling operation of the transmission section <b>20</b> and the reception section <b>30</b>. In the following, the components are described individually.

p-0092First, the configuration of the sensor section <b>10</b> is described with reference to <figref idrefs="DRAWINGS">FIGS. 1 and 2</figref>. <figref idrefs="DRAWINGS">FIG. 2</figref> is a cross sectional view as viewed from along the direction indicated by an arrow marked X in <figref idrefs="DRAWINGS">FIG. 1</figref>. Referring first to <figref idrefs="DRAWINGS">FIG. 2</figref>, the sensor section <b>10</b> includes a first glass substrate <b>15</b>, a reception conductor group <b>11</b> including a plurality of reception conductors <b>12</b>, a spacer <b>16</b>, a transmission conductor group <b>13</b> including a plurality of transmission conductors <b>14</b>, and a second glass substrate <b>17</b>. The transmission conductor group <b>13</b>, spacer <b>16</b>, reception conductor group <b>11</b> and second glass substrate <b>17</b> are formed in this order on the first glass substrate <b>15</b>.

p-0093In the first embodiment, a pointer such as a finger or an electrostatic pen is used on the second glass substrate <b>17</b> side, that is, on the side opposite the face of the second glass substrate <b>17</b> that opposes the first glass substrate <b>15</b>. Further, in the first embodiment, a substrate in the form of a sheet or film made of a synthetic resin or the like may be used in place of the first glass substrate <b>15</b> or the second glass substrate <b>17</b>.

p-0094Each of the transmission conductors <b>14</b> and the reception conductors <b>12</b> is formed from a transparent electrode film, for example, of an ITO (Indium Tin Oxide), a copper foil, or the like. The electrode patterns of the transmission conductors <b>14</b> can be formed, for example, in the following manner. First, an electrode film formed from any of the materials described above is formed on the first glass substrate <b>15</b>, for example, by sputtering, vapor deposition or application. Then, the electrode film is etched to form predetermined electrode patterns. Electrode patterns of the reception conductors <b>12</b> can be formed on the second glass substrate <b>17</b> in a similar manner. Where the transmission conductors <b>14</b> and the reception conductors <b>12</b> are formed from a copper foil, it is possible to use an ink jet printer to spray ink including copper particles in predetermined electrode patterns to a glass plate or the like to produce the conductors.

p-0095The spacer <b>16</b> may be formed from a synthetic resin material such as, for example, PVB (Polyvinyl Butyral), EVA (Ethylene Vinyl Acetate), an acrylic-based resin or the like. The spacer <b>16</b> may otherwise be formed from silicon rubber of a high refractive index, that is, from a high dielectric.

p-0096Where the spacer <b>16</b> is formed from a synthetic resin, it can be formed, for example, in the following manner. First, a synthetic resin sheet is sandwiched between the transmission conductors <b>14</b> and the reception conductors <b>12</b>. Then, while evacuation between the conductors is carried out, pressurization and heating are carried out to form the spacer <b>16</b>. As another example, a synthetic resin in the form of liquid may be supplied into a space between the transmission conductors <b>14</b> and the reception conductors <b>12</b>, whereafter it is solidified to form the spacer <b>16</b>.

p-0097Referring back to <figref idrefs="DRAWINGS">FIG. 1</figref>, the transmission conductor group <b>13</b> includes a plurality of transmission conductors <b>14</b> extending in a predetermined direction, indicated by an arrow mark X, and the transmission conductors <b>14</b> are disposed in parallel to each other and in a spaced relationship at a predetermined distance from each other. Meanwhile, the reception conductor group <b>11</b> includes a plurality of reception conductors <b>12</b> extending in a direction perpendicular to the extension direction of the transmission conductors <b>14</b>, that is, in the direction indicated by an arrow mark Y in <figref idrefs="DRAWINGS">FIG. 1</figref>. The reception conductors <b>12</b> are disposed in parallel to each other and in a spaced relationship from each other. The transmission conductors <b>14</b> and the reception conductors <b>12</b> may each be formed from a conductor of a linear or plate shape or some other predetermined shape. In the first embodiment, the transmission conductors <b>14</b> and the reception conductors <b>12</b> are each formed in a linear shape. While in <figref idrefs="DRAWINGS">FIG. 1</figref> the transmission conductors <b>14</b> and the reception conductors <b>12</b> are shown extending perpendicularly to each other, they may otherwise cross each other at an angle other than the right angle, for example, in an obliquely crossing relationship with each other. From an electric characteristic, the reception conductors should be formed with a width smaller than that of the transmission conductors. This will decrease the floating capacitance to thereby reduce noise, which may appear in the reception conductor.

p-0098In the first embodiment, the number of transmission conductors <b>14</b> is 64 and the number of reception conductors <b>12</b> is 128. Further, the disposition distance, that is, the pitch, of both of the transmission conductors <b>14</b> and the reception conductors <b>12</b> is 3.2 mm. However, the present invention is not limited to the configuration just described, and the number and the pitch of each of the transmission conductors <b>14</b> and the reception conductors <b>12</b> is set suitably in accordance with the size of the sensor section <b>10</b>, required detection accuracy, and so forth.

p-0099The transmission conductors <b>14</b> in the transmission conductor group <b>13</b> are represented by indexes n from “0” to “63” in order, beginning with that of the transmission conductors <b>14</b> which is positioned nearest to the reception section <b>30</b>. In the following description, a transmission conductor <b>14</b> corresponding to the index n is referred to as transmission conductor Y_n. The reception conductors <b>12</b> in the reception conductor group <b>11</b> are represented by index m from “0” to “127” in order, beginning with that of the reception conductors <b>12</b>, which is positioned farthest from the transmission section <b>20</b>. In the following description, a reception conductor <b>12</b> corresponding to the index m is referred to as reception conductor X.

p-0100Further, each of the transmission conductor group <b>13</b> and the reception conductor group <b>11</b> is divided into 16 groups or blocks. A group of the transmission conductor group <b>13</b> is hereinafter referred to as transmission block, and a group of the reception conductor group <b>11</b> is hereinafter referred to as detection block.

p-0101The transmission block includes four transmission conductors <b>14</b>. In particular, each transmission block includes four transmission conductors <b>14</b> which are positioned adjacent to each other and have consecutive indexes n. More particularly, in the present embodiment, the transmission conductor group <b>13</b> is divided into blocks {Y₀to Y₃}, {Y₄to Y₇}, . . . , {Y₅₆to Y₅₉} and {Y₆₀to Y₆₃}.

p-0102Similarly, the detection block includes eight reception conductors <b>12</b>. In particular, each detection block includes eight reception conductors <b>12</b> which are positioned adjacent to each other and have consecutive indexes m. More particularly, the reception conductor group <b>11</b> is divided into blocks {X₀to X₇}, {X₈to X₁₅}, . . . , {X₁₁₂to X₁₁₉} and {X₁₂₀to X₁₂₇}.

p-0103However, the present invention is not limited to the configuration just described. The number of conductors in one group, the number of groups, and the form of groups such as the positional relationship of the conductors belonging to the same group may be set suitably in accordance with the size of the sensor section <b>10</b>, the required detection speed, and so forth. Details are hereinafter described.

p-0104The transmission section <b>20</b> includes a transmission conductor selection circuit <b>22</b>, a multi-frequency signal supplying circuit <b>21</b> and a clock generation circuit <b>23</b>. The transmission conductor selection circuit <b>22</b>, multi-frequency signal supplying circuit <b>21</b> and clock generation circuit <b>23</b> are formed in this order from the sensor section <b>10</b> side. The multi-frequency signal supplying circuit <b>21</b> is connected to the clock generation circuit <b>23</b> and controlled by a clock signal output from the clock generation circuit <b>23</b>.

p-0105<figref idrefs="DRAWINGS">FIG. 3</figref> shows an example of a general configuration of the multi-frequency signal supplying circuit <b>21</b>.

p-0106Referring to <figref idrefs="DRAWINGS">FIG. 3</figref>, the multi-frequency signal supplying circuit <b>21</b> in the first embodiment includes a number of periodic signal production sections <b>24</b> equal to the number of the transmission blocks of the reception conductor group <b>11</b>, that is, 16 periodic signal production sections <b>24</b>. The periodic signal production sections <b>24</b> individually produce a periodic signal of a fixed period under the control of the control circuit <b>40</b>. In the first embodiment, the periodic signals produced by the periodic signal production sections <b>24</b> are denoted by indexes i from “0” to “15” in order beginning with that of the periodic signal production sections <b>24</b> that is positioned nearest to the reception section <b>30</b>. The 16 periodic signals have 16 different frequencies different by 10 kHz from each other, for example, from 100 kHz to 250 kHz.

p-0107<figref idrefs="DRAWINGS">FIG. 4</figref> shows a general configuration of the periodic signal production section <b>24</b>. Referring to <figref idrefs="DRAWINGS">FIG. 4</figref>, the periodic signal production section <b>24</b> includes, as principal components thereof, an adder <b>241</b>, a selector <b>242</b>, a D-type flip-flop (hereinafter referred to as D-FF) <b>243</b>, a rectangular wave ROM <b>244</b> and another D-FF <b>245</b>. These components are individually described below.

p-0108The adder <b>241</b> has a pair of input terminals and a single output terminal for outputting a result of arithmetic operation. To one of the input terminals of the adder <b>241</b>, frequency data which is a skipping over number designation signal is input from a register not shown. The frequency data is a digital signal indicative of one frequency within the range from 100 kHz and 250 kHz and is set for each of the periodic signal production sections <b>24</b> by the control circuit <b>40</b>. An arithmetic operation result output from the output terminal of the adder <b>241</b> is input to the D-FF <b>243</b> through the selector <b>242</b>, and an output of the D-FF <b>243</b> is input to the other input terminal of the adder <b>241</b>.

p-0109The selector <b>242</b> has a pair of input terminals and a single output terminal for outputting a result of arithmetic operation. An arithmetic operation result from the adder <b>241</b> is input to one of the input terminals of the selector <b>242</b>. Initial phase data is input from a register (not shown) to the other input terminal of the selector <b>242</b>. The selector <b>242</b> selectively outputs one of the arithmetic operation result and the initial phase data input thereto. The initial phase data is a digital signal representative of, for example, 22.5°, 45° or 90°, and is set for each of the periodic signal production sections <b>24</b> by the control circuit <b>40</b>. In the present embodiment, the initial phase is 0°.

p-0110The D-FF <b>243</b> temporarily retains data input thereto from the selector <b>242</b>. To the D-FF <b>243</b>, also a clock generated by the clock generation circuit <b>23</b> is input. The D-FF <b>243</b> stores data input thereto from the selector <b>242</b> at a timing of an edge of the clock input thereto from the clock generation circuit <b>23</b>. An output of the D-FF <b>243</b> is input to the rectangular wave ROM <b>244</b> and also to the adder <b>241</b>.

p-0111The rectangular wave ROM <b>244</b> is a ROM (Read Only Memory) in which data of, for example, a pseudo rectangular wave of 8 bits×256 samples is stored. In the periodic signal production section <b>24</b>, the control circuit <b>40</b> or a special readout section designates an address of the rectangular wave ROM <b>244</b> in response to a signal input thereto from the D-FF <b>243</b>, based on a clock supplied from the clock generation circuit <b>23</b>, to read out data from the rectangular wave ROM <b>244</b>. If the frequency data and the initial phase data from the registers change, the address of the rectangular wave ROM <b>244</b> from which data is to be output changes, and the frequency data and the initial phase of rectangular wave data to be output from the rectangular wave ROM <b>244</b> also change.

p-0112In order to make it possible to produce a plurality of frequencies, when an address for reading out data from the rectangular wave ROM <b>244</b> is designated, the periodic signal production section <b>24</b> designates the number of addresses to be skipped. Where data of the rectangular wave ROM <b>244</b> is to be read out using, for example, a 2.56-MHz clock without skipping out addresses at all, the frequency of a rectangular wave to be read out becomes 2.56 MHz÷256=10 kHz. Where skipping out addresses is to be carried out by one address to read out data of the rectangular wave ROM <b>244</b> using a 2.56-MHz clock, the frequency of the rectangular wave to be read out is 2.56 MHz÷(256÷2)=20 kHz. In other words, if the number of addresses to be skipped increases, the frequency also increases. The numerical value examples given above are a mere illustration, and the numerical values are not limited to them.

p-0113The D-FF <b>245</b> temporarily retains rectangular wave data input thereto from the rectangular wave ROM <b>244</b>. The D-FF <b>245</b> outputs the temporarily retained rectangular wave data to the transmission conductor selection circuit <b>22</b> based on a clock data supplied thereto from the clock generation circuit <b>23</b>.

p-0114An operation of the periodic signal production section <b>24</b> will now be described. In the periodic signal production section <b>24</b> configured in a manner described above, if a reset signal output from the control circuit <b>40</b> is input to the selector <b>242</b>, then the selector <b>242</b> selects the initial phase. Then, a signal representative of the initial phase selected by the selector <b>242</b> is input to the D-FF <b>243</b>, by which the initial phase is set. The former process (i.e., selection of the initial phase) is carried out earlier than a rising edge of the clock, and the latter process (i.e., inputting of the selected initial phase) is carried out later than the rising edge of the clock.

p-0115Then, the D-FF <b>243</b> inputs a signal representative of the initial phase to the adder <b>241</b> based on a clock generated by the clock generation circuit <b>23</b>. The adder <b>241</b> carries out a process of adding the frequency data, which is a skipping out designation signal, to the signal input thereto from the D-FF <b>243</b> and representative of the initial phase. The adder <b>241</b> outputs a result of arithmetic operation thereof to the D-FF <b>243</b> through the selector <b>242</b>. The arithmetic operation result, that is, the addition value obtained by the addition of the signal of the initial phase and the frequency data, is set in the D-FF <b>243</b>. The addition value is supplied from the D-FF <b>243</b> to the rectangular wave ROM <b>244</b>. Then, an address corresponding to the addition value is designated based on a clock generated by the clock generation circuit <b>23</b>. Data is output from the rectangular wave ROM <b>244</b> in response to the designated address. The read out data is output to the transmission conductor selection circuit <b>22</b> through the D-FF <b>245</b>. Thereafter, the loop process from the D-FF <b>243</b> to the adder <b>241</b> is repeated to carry out the addition process for a number of times equal to the number of the frequency data. By repeating a sequence of operations described above, rectangular wave data of an object frequency and an initial phase are obtained.

p-0116The first embodiment described is directed to a case where the periodic signals to be supplied to the transmission conductors have a rectangular waveform, which is a pulse waveform exhibiting upward and downward potential variations with respect to a reference potential of 0 volt. However, any periodic signal may be used as long as it has a fixed period. For example, the rectangular wave ROM <b>244</b> may be replaced by a sine wave ROM or a pulse wave ROM so as to produce a sine wave or a pulse wave, which is a rectangular wave oscillating between the 0 volt and another potential Vcc or which may be a negative signal having a polarity reversed from that of the rectangular wave. The rectangular wave described above may be regarded as a rectangular wave which oscillates upwardly and downwardly with reference to a potential, which is equal to one half the potential Vcc of the pulse wave. The periodic signal production section <b>24</b> may naturally be implemented without using various ROMS as described above.

p-0117Further, although, in the first embodiment, the initial phase of the periodic signals is set to 0°, and any of the initial phase and the frequency is not changed after it is set once, the frequency and the initial phase of the frequency signals to be produced by the periodic signal production section <b>24</b> are not limited to those of the example just described. Although the periodic signal production section <b>24</b> outputs the periodic signal at a certain timing, the periodic signal production section <b>24</b> is not limited to that example. Other examples are hereinafter described.

p-0118The selected one of the transmission conductors <b>14</b>, to which a periodic signal is to be supplied, is changed over by the transmission conductor selection circuit <b>22</b> under the control of the control circuit <b>40</b>. The transmission conductor selection circuit <b>22</b> in the first embodiment is formed of a number of switches equal to the number of groups of the transmission conductor group <b>13</b>, that is, of 16 switches.

p-0119<figref idrefs="DRAWINGS">FIG. 5</figref> shows an internal configuration of the transmission conductor selection circuit <b>22</b>. Referring to <figref idrefs="DRAWINGS">FIG. 5</figref>, the transmission conductor selection circuit <b>22</b> includes a plurality of switches <b>22</b><i>a </i>for selectively supplying a periodic signal supplied thereto from the multi-frequency signal supplying circuit <b>21</b>. The switches <b>22</b><i>a </i>are provided in a one-by-one corresponding relationship to transmission blocks <b>25</b>. Each of the switches <b>22</b><i>a </i>has four terminals <b>22</b><i>b </i>on the output side thereof, which are individually connected to corresponding ones of the transmission conductors <b>14</b>. Each of the switches <b>22</b><i>a </i>has one terminal <b>22</b><i>c </i>on the input side thereof, which is connected to an output terminal of a corresponding one of the periodic signal production sections <b>24</b> of the multi-frequency signal supplying circuit <b>21</b> shown in <figref idrefs="DRAWINGS">FIG. 3</figref>. Each of the switches <b>22</b><i>a </i>connects, at a predetermined interval of time, a selected one of the transmission conductors <b>14</b> and a terminal of a corresponding one of the periodic signal production sections <b>24</b>, which outputs a frequency signal of a predetermined frequency f_k(k=0 to 15), to each other. The changeover (switching) operation of the switches <b>22</b><i>a </i>is controlled by the control circuit <b>40</b>.

p-0120<figref idrefs="DRAWINGS">FIG. 6</figref> illustrates an example of the changeover (switching) operation of the transmission conductors <b>14</b> in the first embodiment. Referring to <figref idrefs="DRAWINGS">FIG. 6</figref>, the selected one of the transmission conductors <b>14</b>, which has the highest index in each of the transmission blocks <b>25</b>, that is, the transmission conductor Y₃, Y₇, . . . , Y₅₉or Y₆₃, is connected to an output terminal of a corresponding one of the periodic signal production sections <b>24</b> through a switch <b>22</b><i>a </i>as illustrated in <figref idrefs="DRAWINGS">FIG. 5</figref>.

p-0121Then, the periodic signals output from the periodic signal production sections <b>24</b> of the multi-frequency signal supplying circuit <b>21</b> and having frequencies different from each other are supplied at the same time to 16 transmission conductors <b>14</b> selected by the switches <b>22</b><i>a </i>of the transmission blocks <b>25</b>. In this state, position detection of a pointer is carried out for a predetermined period of time. After the predetermined period of time passes, the switches <b>22</b><i>a </i>change over to be connected to adjacent ones of the transmission conductors <b>14</b> positioned in the direction in which the index n decreases, that is, to the transmission conductors Y₂, Y₆, . . . , Y₅₈and Y₆₂. Then, frequency signals output from the periodic signal production sections <b>24</b> of the multi-frequency signal supplying circuit <b>21</b> and having different frequencies are supplied at the same time to the 16 transmission conductors <b>14</b> after the changeover to carry out position detection. This series of operations is repeated to carry out position detection of at least one pointer.

p-0122After those transmission conductors <b>14</b>, which have the lowest indexes in the individual transmission blocks <b>25</b>, that is, the transmission conductors Y₀, Y₄, . . . , Y₅₆and Y₆₀, are selected by the switches <b>22</b><i>a </i>to carry out position detection of the pointer, those transmission conductors <b>14</b> having the highest indexes in the individual transmission blocks <b>25</b> are again selected by the switches <b>22</b><i>a</i>, and the series of operations described above are repeated in the individual groups. At this time, those transmission conductors <b>14</b>, which are not selected by the switches <b>22</b><i>a </i>are preferably connected to an arbitrary reference potential or the ground potential. Where the transmission conductors, which are not selected by the switches <b>22</b><i>a</i>, are connected to an arbitrary reference potential or the ground potential such that noise, which may otherwise appear in those non-selected transmission conductors, can be minimized. Consequently, the noise resisting property can be improved. The procedure of the changeover (switching) operation of the transmission conductors <b>14</b> is not limited to the example described above with reference to <figref idrefs="DRAWINGS">FIG. 6</figref>. Modification is hereinafter described in detail.

p-0123As described above, in the transmission section <b>20</b>, the plural transmission conductors <b>14</b> are divided into a plurality of groups, each including a predetermined number M (M is an integer equal to or greater than 2 (M≧2); in the example of <figref idrefs="DRAWINGS">FIG. 5</figref>, M=4) of conductors. The supply signals, that is, periodic signals of different frequencies produced by the multi-frequency signal supplying circuit <b>21</b> are supplied to predetermined transmission conductors <b>14</b>, which form the groups, and are successively changed over to be supplied to adjacent conductors in the individual groups. Since the transmission section <b>20</b> is configured in a manner described above, periodic signals for position detection can be supplied at the same time to a plurality of transmission conductors <b>14</b>. Because, in the example described, 16 different frequencies are utilized at the same time, the time required for transmission of a signal for position detection can be reduced to 1/16 of that according to the prior art.

p-0124In this embodiment, where the frequency increases from f₀toward f₁₅, if a comparatively low frequency (for example, f₀) is supplied to a transmission conductor positioned at a comparatively remote position from the reception section <b>30</b> and a comparatively high frequency (for example, f₁₅) is supplied to a transmission conductor positioned at a comparatively near position to the reception section <b>30</b>, a high reception sensitivity is obtained.

p-0125Referring back to <figref idrefs="DRAWINGS">FIG. 1</figref>, the reception section <b>30</b> includes a reception conductor selection circuit <b>31</b>, an amplification circuit <b>32</b>, an A/D (Analog to Digital) conversion circuit section <b>33</b>, a signal detection circuit <b>34</b> and a position calculation circuit <b>35</b>. The reception conductor selection circuit <b>31</b>, amplification circuit <b>32</b>, A/D conversion circuit <b>33</b>, signal detection circuit <b>34</b> and position calculation circuit <b>35</b> are disposed in this order from the sensor section <b>10</b> side.

p-0126The reception conductor selection circuit <b>31</b> in the first embodiment includes a number of switches equal to the number of detection blocks of the reception conductor group <b>11</b>, that is, 16 switches.

p-0127<figref idrefs="DRAWINGS">FIG. 7</figref> shows a general configuration of the reception conductor selection circuit <b>31</b> and associated elements. Referring to <figref idrefs="DRAWINGS">FIG. 7</figref>, the reception conductor selection circuit <b>31</b> includes a plurality of switches <b>31</b><i>a</i>. The switches <b>31</b><i>a </i>are provided in a one-by-one corresponding relationship with the detection blocks <b>36</b>. Each of the switches <b>31</b><i>a </i>has eight terminals <b>31</b><i>b </i>on the input side thereof, which are connected to corresponding ones of the reception conductors <b>12</b>. Each of the switches <b>31</b><i>a </i>has a terminal <b>31</b><i>c </i>on the output side thereof, which is connected to an input terminal of a corresponding one of I/V conversion circuits <b>32</b><i>a </i>hereinafter described. Further, each of the switches <b>31</b><i>a </i>changes over between the reception conductors <b>12</b>, which is to be connected to the corresponding I/V conversion circuit <b>32</b><i>a</i>. Outputs of the I/V conversion circuits <b>32</b><i>a </i>are output to a changeover switch <b>32</b><i>d. </i>

p-0128The changeover switch <b>32</b><i>d </i>successively changes over between the I/V conversion circuits <b>32</b><i>a</i>, which is to be connected to the A/D conversion circuit <b>33</b> after every predetermined interval of time to output voltage signals time-divisionally to the A/D conversion circuit <b>33</b>. Where the configuration just described is used, it is necessary to provide only one system of an A/D conversion circuit <b>33</b> and a circuit group (synchronous detection circuit <b>37</b> and so forth), which is disposed at a succeeding stage to the A/D conversion circuit <b>33</b> in the reception section <b>30</b>. Therefore, the circuit configuration of the reception section <b>30</b> is simple. The changeover switch <b>32</b><i>d </i>may be provided either in the amplification circuit <b>32</b> or in the A/D conversion circuit <b>33</b>.

p-0129<figref idrefs="DRAWINGS">FIG. 8</figref> illustrates changeover (switching) operation of the reception conductors <b>12</b> by the switches <b>31</b><i>a</i>. Referring to <figref idrefs="DRAWINGS">FIG. 8</figref>, the changeover operation of each of the switches <b>31</b><i>a </i>is controlled by the control circuit <b>40</b>. In this example, it is assumed that the switches <b>31</b><i>a </i>in the detection blocks <b>36</b> are first connected to those reception conductors <b>12</b> having the lowest indexes, that is, to the reception conductors X₀, X₈, . . . , X₁₁₂and X₁₂₀, as seen in <figref idrefs="DRAWINGS">FIG. 7</figref>. In this state, position detection of a pointer is carried out at the same time by those reception conductors <b>12</b>, which are currently selected, for a predetermined period of time to obtain output signals S₀, S₁, . . . , S₁₅of the individual groups.

p-0130When the predetermined period of time elapses, the switches <b>31</b><i>a </i>change over the connection of the reception conductors <b>12</b> to adjacent ones of the reception conductors <b>12</b> which are positioned in the direction in which the index m increases, that is, to the reception conductors X₁, X₉, . . . , X₁₁₃and X_12i. Then, output signals output from the reception conductors X₁, X₉, . . . , X₁₁₃and X₁₂₁connected to the switches <b>31</b><i>a </i>after the changeover, that is, output signals S₀, S₁, . . . , S₁₅of the individual groups, are obtained. Thereafter, the switches <b>31</b><i>a </i>repeat this sequence of operations to carry out position detection of the pointer.

p-0131Then, the switches <b>31</b><i>a </i>are connected to the reception conductors <b>12</b> having the highest indexes in the individual detection blocks <b>36</b>, that is, to the reception conductors X₇, X₁₅, . . . , X₁₁₉and X₁₂₇, and position detection of a pointer is carried out at the same time by the reception conductors <b>12</b>. Thereafter, the switches <b>31</b><i>a </i>are again connected to the reception conductors <b>12</b> having the lowest indexes in the individual detection blocks <b>36</b>, and the operations described above are repeated in the individual blocks. At this time, those reception conductors <b>12</b> which are not selected by the switches <b>31</b><i>a </i>are preferably connected to an arbitrary reference potential or the ground potential. Where the reception conductors, which are not selected by the switches <b>31</b><i>a</i>, are connected to an arbitrary reference potential or the ground potential, noise, which may otherwise appear in the non-selected reception conductors, can be minimized Consequently, the noise resisting property can be improved. The changeover (switching) operation of the reception conductors <b>12</b> is not limited to the example described above with reference to <figref idrefs="DRAWINGS">FIG. 8</figref>. Modification is hereinafter described in detail.

p-0132As described above, in the reception section <b>30</b>, the reception conductors <b>12</b> are divided into a plurality of groups, each including a plurality of conductors. Then, at least one conductor which forms each group is selected, and the conductor to be selected is successively changed over among the conductors which form each group. In the configuration just described, multiple output signals for position detection can be obtained at the same time from the reception conductor group <b>11</b>. Since the reception conductor group <b>11</b> is divided into 16 groups, the time required for reception of a signal for position detection can be reduced to 1/16 of that of the prior art.

p-0133The amplification circuit <b>32</b> acquires current signals output from the reception conductors <b>12</b>, converts the current signals into voltage signals, and amplifies the voltage signals. Referring to <figref idrefs="DRAWINGS">FIG. 7</figref>, the amplification circuit <b>32</b> includes a number of I/V conversion circuits <b>32</b><i>a </i>equal to the number of detection groups of the reception conductor group <b>11</b>, that is, 16 UV conversion circuits <b>32</b><i>a</i>. The amplification circuit <b>32</b> also includes a changeover circuit <b>32</b><i>d</i>. One I/V conversion circuit <b>32</b><i>a </i>is connected to each of the detection blocks <b>36</b>. In the present embodiment, each of the I/V conversion circuits <b>32</b><i>a </i>includes an amplifier <b>32</b><i>b </i>in the form of an operational amplifier having one input and one output, and a capacitor <b>32</b><i>c </i>connected to the amplifier <b>32</b><i>b</i>. A resistance element, a transistor, or the like, may be connected in parallel to the capacitor <b>32</b><i>c </i>in order to adjust the dc bias (omitted in <figref idrefs="DRAWINGS">FIG. 7</figref>).

p-0134The A/D conversion circuit <b>33</b> is connected to the amplification circuit <b>32</b> and converts an analog signal output from the amplification circuit <b>32</b> into a digital signal. An A/D converter known in the art may be used for the A/D conversion circuit <b>33</b>.

p-0135Referring back to <figref idrefs="DRAWINGS">FIG. 1</figref>, the signal detection circuit <b>34</b> is connected to the A/D conversion circuit <b>33</b> and detects, from within an output signal from the A/D conversion circuit <b>33</b>, a signal of an object frequency from a plurality of signals of different frequencies produced by the multi-frequency signal supplying circuit <b>21</b>. More particularly, the signal detection circuit <b>34</b> determines a cross point and the level of the detection signal at the cross point. Then, the signal detection circuit <b>34</b> connects the levels of such detection signals between adjacent ones of the cross points and calculates a level curved surface of a mountain shape which exhibits an apex or peak at the cross point [X_n, Y_n], at which the pointer touches. Then, the signal detection circuit <b>34</b> outputs the level curved surface as bit map data to the position calculation circuit <b>35</b>.

p-0136Referring to <figref idrefs="DRAWINGS">FIG. 9</figref>, the signal detection circuit <b>34</b> includes a signal detection section <b>34</b><i>a </i>having a number of synchronous detection circuits <b>37</b> equal to the number of the periodic signals, that is, 16 synchronous detection circuits <b>37</b>, corresponding to the periodic signal production sections <b>24</b>. The signal detection section <b>34</b><i>a </i>is connected at an input terminal thereof to an output terminal of the A/D conversion circuit <b>33</b>. In the example of <figref idrefs="DRAWINGS">FIG. 7</figref>, the changeover switch <b>32</b><i>d</i>, which functions as a circuit for time-divisional selection, is provided on the output side of the I/V conversion circuit <b>32</b><i>a</i>. However, the changeover switch <b>32</b><i>d </i>may be replaced by a number of A/D conversion circuits equal to the number of the detection blocks <b>36</b>.

p-0137<figref idrefs="DRAWINGS">FIG. 9</figref> illustrates a connection relationship of the I/V conversion circuit <b>32</b><i>a</i>, which forms the amplification circuit <b>32</b>, the A/D conversion circuit <b>33</b>, and the signal detection sections <b>34</b><i>a</i>, which form the signal detection circuit <b>34</b>, and an internal configuration of the signal detection section <b>34</b><i>a</i>. Referring to <figref idrefs="DRAWINGS">FIG. 9</figref>, an I/V conversion circuit <b>32</b><i>a</i>, an A/D conversion circuit <b>33</b> and a signal detection section <b>34</b><i>a </i>are connected in series in this order from the reception conductors <b>12</b> side.

p-0138A current signal output from a reception conductor <b>12</b> is converted into a voltage signal and amplified by the UV conversion circuit <b>32</b><i>a</i>. The amplified signal is input to the A/D conversion circuit <b>33</b>, where it is converted into a digital signal. The digital signal is input to the signal detection section <b>34</b><i>a</i>. Then, the signal detection section <b>34</b><i>a </i>detects, from within the digital signal, a signal of the same frequency as that of the periodic signal output from a corresponding one of the periodic signal production sections <b>24</b> in the multi-frequency signal supplying circuit <b>21</b>.

p-0139The signal detection section <b>34</b><i>a </i>includes a plurality of synchronous detection circuits <b>37</b> and a plurality of registers <b>38</b> individually connected to the synchronous detection circuits <b>37</b>. Each of the registers <b>38</b> is divided into four regions <b>38</b><i>a </i>to <b>38</b><i>d</i>. The registers <b>38</b> correspond to the transmission blocks <b>25</b> of the transmission conductor selection circuit <b>22</b>, and the regions <b>38</b><i>a </i>to <b>38</b><i>d </i>in each of the registers <b>38</b> correspond to transmission conductors in a corresponding one of the transmission blocks <b>25</b>. For example, data obtained by dividing output signals from the reception conductors <b>12</b> corresponding to periodic signals supplied to the transmission conductors Y₆₃to Y₆₀by one of the synchronous detection circuits <b>37</b> is stored into the regions <b>38</b><i>a </i>to <b>38</b><i>d </i>of the register <b>38</b> connected to the synchronous detection circuit <b>37</b>. Instead of dividing each register <b>38</b> into four regions <b>38</b><i>a </i>to <b>38</b><i>d </i>as in the example described above, four independent registers may be provided for one synchronous detection circuit.

p-0140Each of the synchronous detection circuits <b>37</b> detects a signal of an object frequency from within the signal input thereto. The number of synchronous detection circuits <b>37</b> provided is equal to the number of the periodic signals, that is, 16, and the synchronous detection circuits <b>37</b> are connected in parallel to each other. Which one of the frequencies each of the synchronous detection circuits <b>37</b> should detect is controlled in an interlocking relationship with production of the periodic signal of the multi-frequency signal supplying circuit <b>21</b> and changeover (switching) of the transmission conductors <b>14</b> by the transmission conductor selection circuit <b>22</b> based on the timing signals inputting from the control circuit <b>40</b>. In the example of <figref idrefs="DRAWINGS">FIG. 9</figref>, the synchronous detection circuits <b>37</b> are represented by indexes j from “0” to “15” in order beginning with that of the synchronous detection circuits <b>37</b> that is positioned remote from the A/D conversion circuit <b>33</b>. In the following description, a synchronous detection circuit <b>37</b> corresponding to the index j is referred to as DCT. The synchronous detection circuits <b>37</b> at the first to 16th stages (DCT₀to DCT₁₅) are connected at an input terminal thereof to the output terminal of the A/D conversion circuit <b>33</b>. DCT means “discrete cosine transform.”

p-0141<figref idrefs="DRAWINGS">FIG. 10</figref> shows a general configuration of the synchronous detection circuit <b>37</b>. Referring to <figref idrefs="DRAWINGS">FIG. 10</figref>, the synchronous detection circuit <b>37</b> includes, as principal components thereof, an input terminal <b>370</b>, a signal source <b>371</b> for generating a frequency signal of a frequency f_kthat is the object of detection, a multiplier <b>373</b> and an integrator <b>374</b>. If a detection signal or an output signal is input from a reception conductor <b>12</b> to the synchronous detection circuit <b>37</b> through the A/D conversion circuit <b>33</b>, it is supplied to the multiplier <b>373</b> of the synchronous detection circuit <b>37</b> through the input terminal <b>370</b>. A periodic signal having a frequency f_kis input from the signal source <b>371</b> to the multiplier <b>373</b>, and the detection signal and the periodic signal of the frequency f_kare multiplied to detect an object signal. Then, the detection signal is input to the integrator <b>374</b>, where it is temporally integrated and output.

p-0142Where the frequency f_kof the periodic signal to be generated by the signal source <b>371</b> is set in this manner, a signal or signal component of the object frequency can be detected. A noise signal has a characteristic that, if an output for a fixed period of time is integrated, components having frequencies different from the frequency f_kare suppressed significantly. Therefore, if a signal component and noise components included in an output signal are integrated for a fixed period of time using the integrator <b>374</b>, the signal component is amplified while the noise components cancel each other and are compressed.

p-0143If a π/2 phase shifter is used to shift the phase of the detection signal by π/2 to carry out detection, it is possible to detect a frequency signal of the frequency f_khaving a phase displaced by π/2 from the signal component included in the detection signal. In other words, a DFT (Discrete Fourier Transform) configuration may be used, and this configuration may be preferable in a pointer detection apparatus that uses an electrostatic pen, in that a detectable phase range is expanded.

p-0144Referring back to <figref idrefs="DRAWINGS">FIG. 9</figref>, the number of registers <b>38</b> is equal to the number of the transmission conductors <b>14</b> (Y₀to Y₆₃) similarly to the synchronous detection circuits <b>37</b>, and the registers <b>38</b> are individually connected to the synchronous detection circuits <b>37</b> (DCT₀to DCT₁₅). The registers <b>38</b> (regions <b>38</b><i>a </i>to <b>38</b><i>d</i>) retain signals detected by the corresponding synchronous detection circuits <b>37</b>, and the signals retained in the registers <b>38</b> are read out to the position calculation circuit <b>35</b> based on timing signals from the control circuit <b>40</b>.

p-0145Referring back to <figref idrefs="DRAWINGS">FIG. 1</figref>, the position calculation circuit <b>35</b> detects, from signals sent from the register <b>38</b> (regions <b>38</b><i>a </i>to <b>38</b><i>d</i>) of the synchronous detection circuits <b>37</b>, a reception conductor <b>12</b>, from which a signal which exhibits a dropped signal level is output, and a frequency of the signal. Then, the position calculation circuit <b>35</b> calculates the position of the pointer based on the index m (0 to 127) of the reception conductor <b>12</b> specified from the signal read out from the register <b>38</b> and the index n (0 to 63) of the transmission conductor <b>14</b> from which the corresponding periodic signal is supplied. The series of operations by the synchronous detection circuit <b>37</b> described above are carried out for the entire reception conductor group <b>11</b> in an interlocking relationship. A periodic signal is produced by the multi-frequency signal supplying circuit <b>21</b> and changeover of the transmission conductor <b>14</b> is carried out by the transmission conductor selection circuit <b>22</b>. The position calculation circuit <b>35</b> outputs not only the position (coordinate) of a cross point, at which a pointer is placed, but also information of the surface area of the sensor section <b>10</b> over which the pointer is placed, and the pressure applied to the sensor section <b>10</b> by the pointer.

p-0146[Principle of Position Detection]

p-0147Now, the principle of position detection of a pointer by the pointer detection apparatus of the present embodiment will be described. As described above, the detection system of the present embodiment is an electrostatic coupling system of the cross point type. It detects the position of a pointer based on a variation of the electrostatic coupling state between the transmission conductors and the reception conductors of the sensor section.

p-0148An electrostatic coupling state between a transmission conductor <b>14</b> and a reception conductor <b>12</b> varies depending upon whether a pointer exists on the sensor section <b>10</b>. <figref idrefs="DRAWINGS">FIG. 11A</figref> illustrates an electrostatic coupling state between a transmission conductor <b>14</b> and a reception conductor <b>12</b> where no pointer exists on the sensor section <b>10</b>, and <figref idrefs="DRAWINGS">FIG. 11B</figref> illustrates an electrostatic coupling state between the transmission conductor <b>14</b> and the reception conductor <b>12</b> where a pointer exists on the sensor section <b>10</b>.

p-0149If a pointer does not exist on the sensor section <b>10</b>, as seen in <figref idrefs="DRAWINGS">FIG. 11A</figref>, the transmission conductor <b>14</b> and the reception conductor <b>12</b> are capacitively coupled to each other through the spacer <b>16</b>, and an electric field emerging from the transmission conductor <b>14</b> converges to the reception conductor <b>12</b>. As a result, current of a predetermined value flows between the transmission conductor <b>14</b> and the reception conductor <b>12</b>.

p-0150However, if a finger <b>19</b> as a pointer exists on the sensor section <b>10</b>, as seen in <figref idrefs="DRAWINGS">FIG. 11B</figref>, the reception conductor <b>12</b> is capacitively coupled not only to the transmission conductor <b>14</b> but also to the ground through the finger <b>19</b>. In the state just described, part of an electric field emerging from the transmission conductor <b>14</b> converges to the finger <b>19</b> and part of current flowing between the transmission conductor <b>14</b> and the reception conductor <b>12</b> flows to the ground through the finger <b>19</b>. As a result, the value of current flowing into the reception conductor <b>12</b> decreases. In the electrostatic coupling system, a variation of the value of current output from the reception conductor <b>12</b> is detected by the reception section <b>30</b> to detect the position of the pointer.

p-0151A position detection where a finger <b>19</b> is placed on a plurality of cross points of the sensor section <b>10</b> at the same time will now be described with reference to <figref idrefs="DRAWINGS">FIGS. 12A to 12D</figref>.

p-0152<figref idrefs="DRAWINGS">FIG. 12A</figref> shows the pointer detection apparatus <b>100</b> where a finger <b>19</b> is placed at a point (grid) of a certain transmission conductor and a certain reception conductor of the sensor section <b>10</b>. Here, as an example, attention is directed to cross points between the transmission conductor Y₆and the reception conductor X₄and between the transmission conductor Y₆and the reception conductor X₁₂₂. <figref idrefs="DRAWINGS">FIG. 12B</figref> illustrates output signals of the reception conductor X₄and the reception conductor X₁₂₂on the transmission conductor Y₆. <figref idrefs="DRAWINGS">FIG. 12C</figref> illustrates a detection waveform of an output signal of the reception conductor X₇on the transmission conductor Y₅₈. <figref idrefs="DRAWINGS">FIG. 12D</figref> illustrates a detection waveform of an output signal from the reception conductor X₇on the transmission conductor Y₂.

p-0153As described above, if a finger <b>19</b> does not exist on the sensor section <b>10</b>, output current from the reception conductor <b>12</b> has a predetermined value. However, if a finger <b>19</b> is placed in proximity to the cross points between the transmission conductor Y₆and the reception conductor X₄and between the transmission conductor Y₆and the reception conductor X₁₂₂, the electrostatic coupling state between the transmission conductor Y₆and the reception conductor X₄, and between the transmission conductor Y₆and the reception conductor X₁₂₂varies as described above with reference to <figref idrefs="DRAWINGS">FIGS. 11A and 11B</figref>. Consequently, the current flowing into the reception conductors X₄and X₁₂₂at the cross points varies. Thereupon, the frequency f₁of the current output from the reception conductor X₄and the reception conductor X₁₂₂corresponds to the frequency f₁of the periodic signal supplied to the transmission conductor Y₆.

p-0154The reception conductor X₄has a detection order number of five in the detection block <b>36</b> (refer to <figref idrefs="DRAWINGS">FIG. 7</figref>), and the reception conductor X₁₂₂has a detection order number of three in the detection block <b>36</b> (refer to <figref idrefs="DRAWINGS">FIG. 7</figref>). Therefore, the synchronous detection circuit <b>37</b> detects the output signal of the reception conductor X₁₂₂with the same frequency as that of the periodic signal supplied to the transmission conductor <b>14</b> at a certain clock time, and then detects the output signal of the reception conductor X₄with the same frequency after an interval of two clocks. The output signals of the reception conductor X₄and the reception conductor X₁₂₂have a decreased level and the position of the finger can be detected in this manner.

p-0155If multiple fingers <b>19</b> are placed on a plurality of cross points along one of the reception conductors <b>12</b> of the sensor section <b>10</b>, the positions can be detected similarly. A detection operation where multiple fingers are placed on a plurality of cross points along the same reception conductor <b>12</b> is described below.

p-0156It is assumed that fingers <b>19</b> are placed on the transmission conductor Y₅₈and Y₂along the reception conductor X₇of the sensor section <b>10</b>, as seen in <figref idrefs="DRAWINGS">FIG. 12A</figref>. A periodic signal of a frequency f₁₄is supplied to the transmission conductor Y₅₈, while another synchronizing signal of the frequency f_ais supplied to the transmission conductor Y₂. Here, the transmission conductor Y₅₈has a supplying order number of three in the corresponding transmission block <b>25</b>, as shown in <figref idrefs="DRAWINGS">FIG. 5</figref>, and the transmission conductor Y₂also has a supplying order number of three in the corresponding transmission block <b>25</b>, as shown in <figref idrefs="DRAWINGS">FIG. 5</figref>. Therefore, an output signal of the reception conductor X₇is detected simultaneously, with the frequencies f₁₄and f₀of the periodic signals supplied to the transmission conductors <b>14</b>, by the DCTs DCT₁₄and DCT₀of the synchronous detection circuits <b>37</b>. In this manner, it is detected that the levels of the output signals of the reception conductor X₇with respect to the transmission conductor Y₅₈and the reception conductor X₇with respect to the transmission conductor Y₂decrease as seen in <figref idrefs="DRAWINGS">FIGS. 12C and 12D</figref>, respectively, and thus the positions of the fingers can be specified.

p-0157In the cross point type electrostatic coupling system configured in a manner described above, the position of a finger <b>19</b> can be specified by detecting the index n (0 to 63) of the transmission conductor <b>14</b>, to which a periodic signal is applied, and the index m (0 to 127) of the reception conductor <b>12</b>, on which reduction of the output signal is detected. On the other hand, in the projection type electrostatic coupling system, where fingers may overlap with each other, it is impossible to specify the positions of the fingers.

p-0158It is to be noted that, when the supplying order of periodic signals to the transmission conductors <b>14</b> differs depending upon the place of a cross point (transmission conductor), the order in which a variation of current flowing to the cross points can be detected through the same reception conductor <b>12</b> becomes different. In other words, the timing at which variations of current flowing to the cross points are detected is not always the same, as in the case just described above wherein the fingers <b>19</b> are placed on the transmission conductors Y₅₈and Y₂along the reception conductor X₇.

p-0159Where a finger <b>19</b> is placed over a plurality of successive cross points of the sensor section <b>10</b>, the position of the finger <b>19</b> can be detected in accordance with a principle similar to that described above. In this instance, the positions of the cross points to be detected appear successively, and a region in which the finger <b>19</b> is placed over can be detected. In other words, the shape of the finger <b>19</b> placed on the sensor section <b>10</b> can be estimated. Therefore, in the present embodiment, not only the position of a pointer disposed on the sensor section <b>10</b>, but also the shape of the pointer placed at the sensor section <b>10</b> can be estimated. For example, where the palm is placed on the sensor section <b>10</b>, not only the position of the hand, but also the shape of the palm of the hand can be estimated.

p-0160[Operation of the Pointer Detection Apparatus]

p-0161An operation of the pointer detection apparatus <b>100</b> of the present embodiment will now be described with reference to the drawings. <figref idrefs="DRAWINGS">FIG. 13</figref> illustrates a detection procedure of a pointer by the pointer detection apparatus <b>100</b> of the present embodiment.

p-0162First, each of the periodic signal production sections <b>24</b> in the multi-frequency signal supplying circuit <b>21</b> sets a periodic signal of a frequency allocated thereto by the control circuit <b>40</b> at step S<b>1</b>.

p-0163Then, the reception conductor selection circuit <b>31</b> of the reception section <b>30</b> uses the switches <b>31</b><i>a </i>to select a predetermined reception conductor <b>12</b> in each of the detection blocks <b>36</b>, and connects the selected reception conductors <b>12</b> to the corresponding IN conversion circuits <b>32</b><i>a </i>at step S<b>2</b>.

p-0164Then, the transmission conductor selection circuit <b>22</b> selects one of the transmission conductors <b>14</b>, to which a periodic signal is to be supplied in each of the transmission blocks <b>25</b>, at step S<b>3</b>. The multi-frequency signal supplying circuit <b>21</b> supplies, to the predetermined transmission conductors <b>14</b> selected in the transmission blocks <b>25</b>, corresponding periodic signals at the same time at step S<b>4</b>. The predetermined reception conductors <b>12</b> in the detection blocks <b>36</b> to be selected upon starting the position detection process are preferably selected in advance before the periodic signals are supplied to the transmission conductor group <b>13</b>.

p-0165Then, the reception section <b>30</b> detects output current from the predetermined reception conductors <b>12</b> selected at step S<b>2</b> at the same time at step S<b>5</b>. In particular, the amplification circuit <b>32</b> first converts the output current from the selected predetermined reception conductors <b>12</b>, that is, from the 16 reception conductors <b>12</b>, into voltages, amplifies the voltages, and outputs the amplified signals to the A/D conversion circuit <b>33</b>. At this time, the output current is converted into voltages by the IN conversion circuits <b>32</b><i>a </i>connected to the reception conductors <b>12</b> and amplified. Thereafter, the A/D conversion circuit <b>33</b> A/D converts the input voltage signals and outputs the resulting digital signals to the signal detection circuit <b>34</b>.

p-0166Then, the signal detection circuit <b>34</b> synchronously detects the different frequency components from the digital signals input thereto at step S<b>6</b>. In particular, the signal detection sections <b>34</b><i>a </i>connected to the A/D conversion circuit <b>33</b> detect signals of the same frequencies as the frequencies supplied to the transmission conductors <b>14</b> from the signals detected through the corresponding reception conductors <b>12</b>. Then, the signal detection circuit <b>34</b> stores the signals calculated with regard to the predetermined reception conductors <b>12</b> into the registers <b>38</b> (regions <b>38</b><i>a </i>to <b>38</b><i>d</i>) at step S<b>7</b>.

p-0167Then, the control circuit <b>40</b> decides at step S<b>8</b> whether or not the position detection with regard to all transmission conductors <b>14</b> ends on the reception conductors <b>12</b> selected at step S<b>2</b>. If the position detection with regard to all transmission conductors <b>14</b> does not end on the selected reception conductors <b>12</b>, that is, if the result of the decision at step S<b>8</b> is NO, then the processing returns to step S<b>3</b>, at which the switches <b>22</b><i>a </i>in the transmission blocks <b>25</b> in the transmission conductor selection circuit <b>22</b> are changed over to select the transmission conductors <b>14</b> different from those in the preceding operation cycle. Then, multi-frequency signals are supplied simultaneously from the multi-frequency signal supplying circuit <b>21</b> to the selected transmission conductors <b>14</b>. Thereafter, the processes at steps S<b>3</b> to S<b>7</b> are repeated until the position detection with regard to all transmission conductors <b>14</b> ends on the selected reception conductors <b>12</b>. If the position detection with regard to all transmission conductors <b>14</b> ends on the selected reception conductors <b>12</b>, the signals at all cross points on the reception conductors <b>12</b> stored in the registers <b>38</b> are read out into the position calculation circuit <b>35</b>.

p-0168Referring to <figref idrefs="DRAWINGS">FIGS. 1</figref>, <b>5</b> and <b>7</b>, for example, when the reception conductors X₀, X₈, . . . , and X₁₂₀are selected, periodic signals are supplied to the transmission conductors Y₃, Y₇, . . . , and Y₆₃to carry out position detection. Then, at a next clock signal, while the reception conductors remain selected, periodic signals are supplied this time to the transmission conductors Y₂, Y₆, . . . , and Y₆₂to carry out position detection. This process is repeated until periodic signals are supplied to the transmission conductors Y₀, Y₄, . . . , and Y₆₀to carry out position detection. At this time, a full cycle of the changeover (switching) of transmission conductors in each group is completed, and the position detection of all transmission conductors <b>14</b> regarding the reception conductors X₀, X₈, . . . , and X₁₂₀is completed. This is a state when the result of the decision at step S<b>8</b> is YES. If the detection of all transmission conductors with regard to the selected reception conductors is ended in this manner, the processing advances to step S<b>9</b>.

p-0169When the position detection with regard to all transmission conductors <b>14</b> ends on the reception conductors <b>12</b> selected at step S<b>4</b>, that is, if the result of the decision at step S<b>8</b> is YES, then the control circuit <b>40</b> decides at step S<b>9</b> whether or not the position detection with regard to all reception conductors <b>12</b> is completed. If the position detection with regard to all reception conductors <b>12</b> is not completed, (the result of the decision at step S<b>9</b> is NO), the processing returns to step S<b>2</b>, at which the switches <b>31</b><i>a </i>of the detection blocks <b>36</b> in the reception conductor selection circuit <b>31</b> are changed over to select the reception conductors <b>12</b> different from those in the preceding operation cycle. Further, concurrently with the changeover on the reception side, the switches <b>22</b><i>a </i>of the transmission blocks <b>25</b> in the transmission conductor selection circuit <b>22</b> are changed over to select those transmission conductors <b>14</b> which are different from those in the preceding cycle, that is, the same as those selected first at step S<b>3</b>. Then, to the selected transmission conductors <b>14</b>, multi-frequency signals are supplied at the same time from the multi-frequency signal supplying circuit <b>21</b>. In this manner, the reception conductors <b>12</b> and the transmission conductors <b>14</b> are changed over to continue the position detection. Thereafter, the processes at steps S<b>2</b> to S<b>8</b> are repeated until the position detection with regard to the transmission conductors <b>14</b> is completed on all reception conductors <b>12</b>.

p-0170Referring to <figref idrefs="DRAWINGS">FIGS. 1</figref>, <b>5</b> and <b>7</b>, for example, when the reception conductors X₀, X₈, . . . , and X₁₂₀remain selected, the transmission conductor <b>14</b> to be selected in each group is rotated such that position detection of all transmission conductors in each group is carried out with regard to the reception conductors X₀, X₈, . . . , and X₁₂₀. Then, the reception conductors <b>12</b> to be selected are changed over to the reception conductors X₁, X₉, . . . , and X₁₂₁, and the transmission conductor <b>14</b> to be selected in each group is rotated in a manner described above. The sequence of processes described is repeated to successively change over the reception conductors <b>12</b> to be selected. If at the end of the rotation, the position detection with regard to all transmission conductors is completed with respect to the reception conductors X₇, X₁₅, . . . , and X₁₂₇, the processing advances to step S<b>10</b>, but if the position detection is not completed, the processing returns to step S<b>2</b>.

p-0171The position calculation circuit <b>35</b> detects, from the signals at the cross points of the reception conductors <b>12</b> input from the synchronous detection circuit <b>37</b>, a reception conductor <b>12</b>, which outputs a signal having a reduced signal level and the frequency of the signal. At step S<b>10</b>, the position calculation circuit <b>35</b> calculates the position of the pointer based on the index m (0 to 127) of the reception conductor <b>12</b> specified from the signal level and the index n (0 to 63) of the transmission conductor <b>14</b> from which the periodic signal is supplied. In the present embodiment, position detection of the pointer disposed on the sensor section <b>10</b> is carried out in this manner.

p-0172As described above, in the first embodiment, signals having different frequencies are supplied simultaneously or multiple-transmitted to predetermined ones of the transmission conductors <b>14</b> in the individual groups, and the position of the pointer is detected at the same time through a predetermined plural number of reception conductors <b>12</b>. In other words, a position detection process is carried out at the same time for a plurality of cross points between the transmission conductors <b>14</b> and the reception conductors <b>12</b>. Therefore, with the present embodiment, the time required for position detection for a plurality of cross points can be reduced and higher speed position detection becomes possible.

p-0173More particularly, in the first embodiment, the transmission conductor group <b>13</b> and the reception conductor group <b>11</b> are each divided into 16 groups and the groups are processed in parallel to each other. Therefore, in the present embodiment, the detection time can be reduced, for example, to 1/(16×16) in comparison with the detection time where a detection process is carried out successively for all cross points as in the prior art. The number of groups is not limited to the specific number mentioned above, and an effect of reduction of the detection time can be obtained even if only one of the transmission conductor group <b>13</b> and the reception conductor group <b>11</b> is divided into groups.

p-0174Further, in the first embodiment described above, after detection ends for all transmission conductors on one reception conductor, the processing-object reception conductor is changed over to a next reception conductor to continue the position detection. However, the position detection is not limited to this configuration. For example, the processing-object reception conductor may be changed over to another reception conductor to continue position detection before the detection with regard to all transmission conditions on one reception conductor is completed. It is only necessary for the position detection to be carried out in the end at all cross points of the sensor section <b>10</b>.

p-0175[Modification 1]

p-0176In the first embodiment described above, the sensor section <b>10</b> is configured such that the reception conductors <b>12</b> and the transmission conductors <b>14</b> between which the spacer <b>16</b> is interposed are formed on one of the surfaces of the first glass substrate <b>15</b>. However, the present invention is not limited to such arrangement. For example, the reception conductors and the transmission conductors may be formed on the opposite faces of one glass substrate. <figref idrefs="DRAWINGS">FIG. 14</figref> shows an example of such configuration.

p-0177In particular, <figref idrefs="DRAWINGS">FIG. 14</figref> shows a schematic cross section of a sensor section according to modification 1.

p-0178Referring to <figref idrefs="DRAWINGS">FIG. 14</figref>, the sensor section <b>50</b> according to modification 1 includes a glass substrate <b>51</b>, a plurality of transmission conductors <b>52</b> formed on one of surfaces of the glass substrate <b>51</b>, on the lower face of the glass substrate <b>51</b> in <figref idrefs="DRAWINGS">FIG. 14</figref>, and a first protective layer <b>53</b> formed on the transmission conductors <b>52</b>. The sensor section <b>50</b> further includes a plurality of reception conductors <b>54</b> formed on the other surface of the glass substrate <b>51</b>, on the upper surface of the glass substrate <b>51</b> in <figref idrefs="DRAWINGS">FIG. 14</figref>, a second protective layer <b>55</b> formed on the reception conductors <b>54</b>, and a protective sheet <b>56</b> formed on the second protective layer <b>55</b>. The detection surface for a pointer in the present example is a surface of the sensor section <b>50</b> on the protective sheet <b>56</b> side.

p-0179In modification 1, the glass substrate <b>51</b>, transmission conductors <b>52</b> and reception conductors <b>54</b> are formed from materials similar to those used in the first embodiment described above. Further, in modification 1, the glass substrate <b>51</b> may be replaced by a sheet-like or film-like substrate formed from a synthetic resin material similarly as in the first embodiment. Further, the first protective layer <b>53</b> and the second protective layer <b>55</b> can be formed, for example, from a SiO₂film or a synthetic resin film, and the protective sheet <b>56</b> may be formed using a sheet member made of, for example, a synthetic resin material.

p-0180Since the sensor section <b>50</b> of modification 1 can reduce the number of glass substrates in comparison with the sensor section <b>10</b> of the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 2</figref>, the thickness of the sensor section <b>50</b> can be further reduced. Further, in the sensor section <b>50</b> of modification 1, since the number of glass substrates can be reduced, a less expensive sensor section can be formed.

p-0181[Modification 2]

p-0182<figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref> illustrate an example of a configuration of a sensor section where transmission conductors and reception conductors are formed on the surface on one side of a glass substrate, as modification 2. In particular, <figref idrefs="DRAWINGS">FIG. 15A</figref> shows a cross section of the sensor section of modification 2 at a cross point, and <figref idrefs="DRAWINGS">FIG. 15B</figref> shows a perspective view of the sensor section of modification 2.

p-0183Referring to <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref>, the sensor section <b>60</b> shown includes a glass substrate <b>61</b>, metal sections <b>62</b> having conductivity and formed in a predetermined pattern on one of the surfaces of the glass substrate <b>61</b>, insulating sections <b>63</b> formed on the metal sections <b>62</b>, a plurality of transmission conductors <b>64</b>, and a plurality of reception conductors <b>65</b>. Although a protective layer and a protective sheet are provided, they are omitted in <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref>.

p-0184The metal sections <b>62</b> are substantially linear metal members formed, for example, by drawing a metal material in a direction perpendicular to the direction in which the reception conductors <b>65</b> extend. The insulating sections <b>63</b> are formed so as to cover over part of the metal sections <b>62</b>. Further, the transmission conductors <b>64</b> are provided at the opposite ends in the drawing direction of the metal sections <b>62</b> and are electrically connected to each other by the metal sections <b>62</b>. The reception conductors <b>65</b> are formed so as to stretch over the insulating sections <b>63</b>, such that the reception conductors <b>65</b> are electrically isolated from the metal sections <b>62</b> and transmission conductors <b>64</b>.

p-0185Although in <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref>, the transmission conductors <b>64</b> are formed in such a manner as to cover over part of the upper surface of the metal sections <b>62</b> and the insulating sections <b>63</b>, the present modification is not limited to the form described. Since the object of the provision of the metal sections <b>62</b> is achieved as long as the transmission conductors <b>64</b> provided at the opposite ends in the extension direction of the metal sections <b>62</b> are electrically connected to each other by the metal sections <b>62</b>, there is no need, for example, for the transmission conductors <b>64</b> to cover over the upper surface of the metal sections <b>62</b>. Similarly, although, in <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref>, the transmission conductors <b>64</b> are shown covering over part of the upper surface of the insulating sections <b>63</b>, the covering state is not limited to this arrangement. It is only necessary for the reception conductors <b>65</b> to be electrically isolated from the transmission conductors <b>64</b> and metal sections <b>62</b>.

p-0186Further, in the example of <figref idrefs="DRAWINGS">FIGS. 15A and 15B</figref>, the detection surface for a pointer may be the surface of the glass substrate <b>61</b> on which the conductors are formed or the face of the glass substrate <b>61</b> opposite to the face on which the conductors are formed.

p-0187In modification 2, the reception conductors <b>65</b> are formed from a linear conductor similar to the first embodiment described above. Meanwhile, the transmission conductors <b>64</b> are formed so as to be connected to the metal sections <b>62</b> through openings in the insulating sections <b>63</b>. In particular, the transmission conductors <b>64</b>, to which periodic signals are supplied, are disposed three-dimensionally such that they pass below the reception conductors <b>65</b> with the insulating sections <b>63</b> sandwiched therebetween.

p-0188Further, in modification 2, the glass substrate <b>61</b>, transmission conductors <b>64</b> and reception conductors <b>65</b> are formed from materials similar to those which are used in the first embodiment described above. In the present example, the glass substrate <b>61</b> may be replaced with a sheet-like or film-like substrate formed from a synthetic resin material similarly as in the first embodiment.

p-0189The metal sections <b>62</b> can be formed from a metal material having a high conductivity such as, for example, Mo (molybdenum) or Al (aluminum). Since the dimension of the connecting portions between the metal sections <b>62</b> and the transmission conductors <b>64</b> is very small, in order to reduce the resistance at the connecting portions, it is preferable to use a metal material having a high conductivity for the metal sections <b>62</b>. Further, the insulating sections <b>63</b> may be formed, for example, from resist.

p-0190With the sensor section <b>60</b> of modification 2, since the number of glass substrates can be reduced in comparison with the sensor section <b>10</b> of the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 2</figref>, the thickness of the sensor section <b>60</b> can be reduced. Further, in the sensor section <b>60</b> of the present example, since the number of glass substrates can be reduced, a less expensive sensor section can be provided. Further, cost reduction occurs also because wiring lines of the transmission conductors and the reception conductors can be formed in the same layer.

p-0191Furthermore, the sensor section <b>60</b> of modification 2 can achieve the following advantage in comparison with the sensor section <b>50</b> of modification 1. In particular, where the face of the glass substrate <b>61</b> on the side opposite to the face, on which the conductors are formed, is used as the detection surface for a pointer in the sensor section <b>60</b> of modification 2, the glass substrate <b>61</b> exists between the pointer and the conductors. In this instance, the distance between the pointer and the conductors increases in comparison with that in the sensor section <b>50</b> of modification 1, and any effect of noise from the pointer decreases.

p-0192[Modification 3]

p-0193In the first embodiment and modifications <b>1</b> and <b>2</b> described above, the transmission conductors and the reception conductors can be individually formed from a linear conductor of a fixed width extending in a predetermined direction. However, the shape of the transmission conductors and the reception conductors in the present invention is not limited to a linear shape extending in a predetermined direction. Another example of a configuration of the transmission conductors is described below as modification 3.

p-0194<figref idrefs="DRAWINGS">FIG. 16A</figref> shows, in an enlarged scale, cross points between transmission conductors and reception conductors in a sensor section of modification 3, and <figref idrefs="DRAWINGS">FIG. 16B</figref> shows a land conductor portion <b>73</b>A in an enlarged scale.

p-0195Referring to <figref idrefs="DRAWINGS">FIGS. 16A and 16B</figref>, in the sensor section <b>70</b>A of modification 3 shown, the reception conductors <b>74</b> are formed from a linear conductor of a fixed width as seen in <figref idrefs="DRAWINGS">FIG. 16A</figref>. However, the transmission conductors <b>71</b>A are formed from a linear conductor portion <b>72</b> and land conductor portions <b>73</b>A having a width greater than that of the linear conductor portion <b>72</b> and made of ITO or the like.

p-0196Referring to <figref idrefs="DRAWINGS">FIG. 16B</figref>, each land conductor portion <b>73</b>A includes first and second land portions <b>73</b><i>b </i>and <b>73</b><i>c </i>formed in a substantially same shape and a substantially linear connecting portion <b>73</b><i>d </i>for electrically connecting the first and second land portions <b>73</b><i>b </i>and <b>73</b><i>c </i>to each other. The first and second land portions <b>73</b><i>b </i>and <b>73</b><i>c </i>are formed in a substantially triangular shape having an apex <b>73</b><i>a</i>, at which the land conductor portion <b>73</b>A is connected to the linear conductor portion <b>72</b>. The first land portion <b>73</b><i>b </i>and the second land portion <b>73</b><i>c </i>are electrically connected to each other at bottom portions <b>73</b><i>e </i>thereof, opposite the apexes <b>73</b><i>a</i>, by the connecting portion <b>73</b><i>d. </i>

p-0197Where the transmission conductor <b>71</b>A is formed in a shape described above, it is provided with an increased area in proximity to the cross point. As a result, when a pointer comes near the sensor section, an electric field emerging from the transmission conductor converges by an increasing amount to the pointer, and therefore, the detection sensitivity is improved.

p-0198Further, the land conductor portion <b>73</b>A is shaped in a substantially H shape such that the first land portion <b>73</b><i>b </i>and the second land portion <b>73</b><i>c </i>are connected to each other by the connecting portion <b>73</b><i>d </i>to provide recesses <b>73</b><i>f </i>therebetween. Thus, if the pointer detection apparatus, to which the present invention is applied, and another pointer detection apparatus, which adopts an electromagnetic resonance system, are placed one on the other to form an inputting apparatus wherein a region for detecting a pointer is formed commonly between the two pointer detection apparatus, eddy current in the transmission conductors resulting from an electric field generated from the position detection apparatus of the electromagnetic resonance system is suppressed. As a result, deterioration of the detection sensitivity of the pointer detection apparatus of the electromagnetic resonance type due to loss caused by the eddy current can be prevented.

p-0199<figref idrefs="DRAWINGS">FIG. 17</figref> shows, in an enlarged scale, a cross point between a transmission conductor and a reception conductor in a sensor section of another example of modification 3.

p-0200Referring to <figref idrefs="DRAWINGS">FIG. 17</figref>, in the sensor section <b>70</b>B of the present example, a transmission conductor <b>71</b>B includes a linear conductor portion <b>72</b> and a land conductor portion <b>73</b>B modified from that in modification 3. The sensor section <b>70</b>B is different from that of modification 3 in that, while the land conductor portion <b>73</b>A in modification 3 has the first and second land portions <b>73</b><i>b </i>and <b>73</b><i>c </i>of a substantially triangular shape, the land conductor portion <b>73</b>A in the present example has first and second land portions <b>73</b><i>g </i>and <b>73</b><i>h </i>having a substantially trapezoidal shape. In the present example, the land conductor portion <b>73</b>B is electrically connected at smaller parallel sides <b>73</b><i>i </i>thereof, which correspond to the apexes <b>73</b><i>a </i>of the first and second land portions <b>73</b><i>b </i>and <b>73</b><i>c </i>in modification 3, to the linear conductor portion <b>72</b>. The remaining part of the sensor section <b>70</b>B is similar to that of the sensor section <b>70</b>A described above with reference to <figref idrefs="DRAWINGS">FIG. 16</figref>, and the description of the common configuration is omitted to avoid redundancy.

p-0201Comparing the present land conductor portion <b>73</b>B to the land conductor portion <b>73</b>A in modification 3, since the land conductor portion <b>73</b>B is shaped such that it has no apex portion <b>73</b><i>a</i>, that is, no sharp (acute) angle portion, the flow path of electric current is wider than that of the land conductor portion <b>73</b>A. As a result, concentration of current upon the connecting portion between the land conductor portion <b>73</b>B and the linear conductor portion <b>72</b> does not occur, and the current disperses. In particular, since current flows in a spread fashion between the smaller parallel sides <b>73</b><i>i</i>, which define the opposite ends of the land conductor portion <b>73</b>B, the resistance value between the smaller parallel sides <b>73</b><i>i </i>does not increase. As a result, the electric conduction characteristic is further improved in comparison with that of the transmission conductors in modification 3 described above with reference to <figref idrefs="DRAWINGS">FIG. 16</figref>. Where the transmission conductors around the cross points of the sensor section are shaped in this manner, the electric conduction characteristic can be further improved. The shape of the smaller parallel side <b>73</b><i>i </i>preferably has no sharp (acute) angle portion and the smaller parallel side <b>73</b><i>i </i>may have, for example, a curved shape different from the shape described above and shown in <figref idrefs="DRAWINGS">FIG. 17</figref>. Further, while the sensor section <b>70</b>B in the present example is configured such that the two recesses <b>73</b><i>f </i>are formed in the land conductor portions <b>73</b>A and <b>73</b>B, the number of such recesses is not limited to two, and four or more recesses may be provided.

p-0202The two examples of modification 3 shown in <figref idrefs="DRAWINGS">FIGS. 16 and 17</figref> can be applied not only in the sensor section of the pointer detection apparatus of the cross point type electrostatic coupling system, but can be applied also in a sensor section of a pointer detection apparatus of the projected capacitive type or some other type. Further, while in modification 3 a unique shape of the land conductor portion of the transmission conductors is proposed, a similar shape may be used to form a land conductor portion on the reception conductors in proximity to the cross points.

p-0203Further, the land conductor portion can be applied to any of the sensor section <b>50</b> formed from two layers in modification 1 described above with reference to <figref idrefs="DRAWINGS">FIG. 14</figref>, and the sensor section <b>60</b> formed from one layer in modification 2 described above with reference to <figref idrefs="DRAWINGS">FIG. 15</figref>. Where the pointer detection apparatus is formed integrally with a display apparatus such as in a liquid crystal panel, in order to suppress the influence of electrostatic noise from the liquid crystal panel, the reception conductors are preferably disposed in a direction crossing the scanning direction of the liquid crystal panel.

p-0204[Modification 4]

p-0205A pointer detection apparatus in a cross point electrostatic coupling system has a region wherein a plurality of reception conductors and a plurality of transmission conductors cross each other and a conductor pattern exists, and another region wherein no conductor exists and no conductor pattern exists, if the sensor section is viewed from the surface of the pointer detection apparatus on which a pointer is to be operated, that is, from above the surface of the pointer detection apparatus. Although the conductors are formed from a transparent electrode film such as an ITO film, the transmission factor in the region in which the conductor pattern exists is lower than that in the region in which no conductor pattern exists. As a result, unevenness of the transmission factor appears on the sensor section. The user may feel uneasy with the unevenness of the transmission factor. Therefore, modification 4 is configured so as to eliminate such unevenness of the transmission factor on the sensor section.

p-0206<figref idrefs="DRAWINGS">FIG. 18</figref> shows a general configuration of the sensor section of modification 4. The configuration of modification 4 is applied to the sensor section <b>50</b> of modification 1 described above with reference to <figref idrefs="DRAWINGS">FIG. 14</figref>. Referring to <figref idrefs="DRAWINGS">FIG. 18</figref>, in the sensor section <b>70</b>C of modification 4, in a region in which none of transmission conductors <b>52</b> and reception conductors <b>54</b> exist, first transparent electrode films <b>333</b> and second transparent electrode films <b>334</b> made of the same material as the conductors are provided. The other part of the sensor section <b>70</b>C has the same configuration as that of the sensor section <b>50</b> of modification 1 described above with reference to <figref idrefs="DRAWINGS">FIG. 14</figref>.

p-0207<figref idrefs="DRAWINGS">FIG. 19A</figref> shows a configuration of a transmission conductor <b>52</b> and a first transparent electrode film <b>333</b> formed on one surface, that is, on the lower surface, of a glass substrate of the sensor section <b>70</b>C. The first transparent electrode film <b>333</b> of a rectangular shape is disposed on the surface of a glass substrate, on which the transmission conductor <b>52</b> is provided, between two transmission conductors <b>52</b> disposed in proximity to each other. The first transparent electrode film <b>333</b> has a dimension a little smaller than the dimension of the distance between the transmission conductors such that it does not contact with any of the transmission conductors <b>52</b>, and is spaced away from the reception conductors <b>52</b> with some air gap left therebetween. The dimension of the first transparent electrode film <b>333</b> in the lengthwise dimension of the transmission conductors <b>52</b> is a little smaller than the dimension of the sum of the distance between the reception conductors <b>54</b> disposed in proximity to each other and the conductor width of one reception conductor <b>54</b>. The first transparent electrode film <b>333</b> is disposed between the two reception conductors <b>54</b> positioned in proximity to each other, and is positioned such that both sides thereof extend to overlap approximately ½ of the conductor width of the reception conductors <b>54</b>.

p-0208<figref idrefs="DRAWINGS">FIG. 19B</figref> shows a configuration of a reception conductor <b>54</b> and a second transparent electrode film <b>334</b> formed on the other surface, that is, on the upper surface, of the glass substrate of the sensor section <b>70</b>C. In the present example, the second transparent electrode film <b>334</b> is disposed on the surface of the glass substrate on which the reception conductor <b>54</b> is disposed. Regarding the dimension of the second transparent electrode film <b>334</b>, an approach similar to that used where the dimension of the first transparent electrode film <b>333</b> is defined can be applied. In particular, the second transparent electrode film <b>334</b> has a little smaller dimension than the dimension between the reception conductors so that it does not contact with the reception conductors <b>54</b>, and is spaced away from the reception conductors <b>54</b> with some air gap left therebetween. Regarding the dimension of the second transparent electrode film <b>334</b> in the lengthwise dimension of the reception conductor <b>54</b>, it is set such that the second transparent electrode film <b>334</b> partly overlaps with part of the transmission conductor <b>52</b> disposed in proximity to each other. The first transparent electrode film <b>333</b> and the second transparent electrode film <b>334</b> should be disposed such that, when the sensor section <b>70</b>C is viewed from the surface side of the sensor section <b>70</b>C on which a pointer is to be operated, that is, from the upper surface side, the superposing relationship of the transmission conductor <b>52</b>, reception conductor <b>54</b>, first transparent electrode film <b>333</b>, and second transparent electrode film <b>334</b> is made as uniform as possible while the electric isolation from each other is maintained. Thus, unevenness of the transmission factor can be suppressed over the entire sensor section <b>70</b>C and a uniform optical characteristic can be maintained.

p-0209If the conductors and the transparent electrode films formed on the surfaces of the glass substrate of the sensor section <b>70</b>C are disposed as seen in <figref idrefs="DRAWINGS">FIGS. 19A and 19B</figref>, then when the sensor section <b>70</b>C is viewed from above, the first transparent electrode films <b>333</b> and the second transparent electrode films <b>334</b> made of the same material as the conductors, are formed also in a region, in which the conductor pattern does not exist (as seen in <figref idrefs="DRAWINGS">FIG. 18</figref>). As a result, unevenness of the transmission factor on the sensor section <b>70</b>C is suppressed.

p-0210The shape of the first transparent electrode film <b>333</b> and the second transparent electrode film <b>334</b> for suppressing unevenness of the transmission factor is not limited to a rectangular shape. It is only necessary that the superposing relationship between the conductor pattern formed from the transparent electrodes, the first transparent electrode films <b>333</b>, and second transparent electrode films <b>334</b>. when the sensor section <b>70</b>C is viewed from above. be optically uniform. The shape of the first transparent electrode films <b>333</b> and the second transparent electrode films <b>334</b> is suitably set in relation to the shape of the conductor pattern formed from the transparent electrode films. For example, a plurality of transparent electrode films of a rectangular shape are disposed in a spaced relationship from each other by a predetermined distance and extend along a direction in which the transmission conductors or the reception conductors extend. However, the plural transparent electrode films may otherwise be formed as a single electrode film.

p-0211[Modification 5]

p-0212While in the first embodiment described above, both of the transmission conductors and the reception conductors are linear conductors and extend perpendicularly to each other, the preset invention is not limited to such arrangement. For example, at least one of the transmission conductors and the reception conductors may be formed from a curved conductor. An example is shown in <figref idrefs="DRAWINGS">FIG. 20</figref>.

p-0213<figref idrefs="DRAWINGS">FIG. 20</figref> shows an arrangement pattern of a transmission conductor group <b>82</b> and a reception conductor group <b>81</b> of a sensor section <b>80</b> according to modification 5. In modification 5, the transmission conductor group <b>82</b> includes a plurality of transmission conductors <b>82</b><i>a </i>individually formed as rings having different diameters from each other. The ring-shaped transmission conductors <b>82</b><i>a </i>are disposed in a concentric relationship with each other such that the distances between adjacent ones of the transmission conductors <b>82</b><i>a </i>in a radius direction are equal to each other.

p-0214Meanwhile, the reception conductor group <b>81</b> includes a plurality of linear reception conductors <b>81</b><i>a </i>formed so as to extend radially from the center of the transmission conductor group <b>82</b>. The reception conductors <b>81</b><i>a </i>are disposed in an equidistantly spaced relationship from each other in a circumferential direction of the concentric circles formed from the transmission conductor group <b>82</b>. While in modification 5 shown in <figref idrefs="DRAWINGS">FIG. 20</figref>, the transmission conductors <b>82</b><i>a </i>are disposed in an equidistantly spaced relationship from each other, the distances between the transmission conductors <b>82</b><i>a </i>need not be equal to each other, but may be set to suitable distances in accordance with an application of the present invention.

p-0215The sensor section <b>80</b> in modification 5 is suitable for detection, for example, of rotational operation.

p-0216[Modification 6]

p-0217While in the first embodiment described above, a one-input one-output amplifier is used for the amplifier <b>32</b><i>b </i>in the amplification circuit <b>32</b> as seen in <figref idrefs="DRAWINGS">FIG. 7</figref>, the present invention is not limited to such configuration. For example, a differential amplifier may be used for the amplifier. An example is shown in <figref idrefs="DRAWINGS">FIGS. 21A and 21B</figref>. In <figref idrefs="DRAWINGS">FIGS. 21A and 21B</figref>, elements like those in the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 7</figref> are denoted by like reference characters and overlapping description of them is omitted herein to avoid redundancy.

p-0218In particular, <figref idrefs="DRAWINGS">FIG. 21A</figref> shows a general configuration of an amplifier according to modification 6, and <figref idrefs="DRAWINGS">FIG. 21B</figref> shows a general configuration of an amplification circuit and peripheral circuits where a differential amplifier is used.

p-0219Referring first to <figref idrefs="DRAWINGS">FIG. 21A</figref>, the differential amplifier <b>85</b> in modification 6 is a two-input one-output differential amplifier. In modification 6, a pair of adjacent ones of reception conductors <b>12</b> are connected one by one to the two input terminals of the differential amplifier <b>85</b>. Further, in modification 6, the reception conductor group <b>11</b> includes 129 reception conductors <b>12</b>. The reception conductor group <b>11</b> is divided into 16 detection blocks <b>36</b>, each including 9 reception conductors <b>12</b>. Each detection block <b>36</b> includes 9 reception conductors <b>12</b> which are positioned adjacent to each other, that is, which have consecutive indexes m. The ninth one of the reception conductors <b>12</b> which has the highest index m in each detection block <b>36</b> is used commonly by an adjacent detection block <b>36</b>. In particular, in modification 6, the reception conductor group <b>11</b> is divided into detection blocks {X₀to X₈}, {X₈to X₁₅}, . . . , {X₁₁₄to X₁₂₁} and {X₁₂₁to X₁₂₈}.

p-0220Referring now to <figref idrefs="DRAWINGS">FIG. 21B</figref>, a reception conductor selection circuit <b>88</b> includes a plurality of pairs of switches <b>88</b><i>a </i>and <b>88</b><i>b</i>. One pair of switches <b>88</b><i>a </i>and <b>88</b><i>b </i>are provided for each one detection block <b>36</b>. The paired switches <b>88</b><i>a </i>and <b>88</b><i>b </i>include nine common input terminals <b>31</b><i>b</i>. The common input terminals <b>31</b><i>b </i>are connected to corresponding ones of the reception conductors <b>12</b>. Terminals <b>88</b><i>c </i>and <b>88</b><i>d </i>of the paired switches <b>88</b><i>a </i>and <b>88</b><i>b </i>on the output side are connected to input terminals of different IN conversion circuits <b>32</b><i>a</i>. The one of the I/V conversion circuits <b>32</b><i>a</i>, which is connected to the output terminal of the switch <b>88</b><i>a</i>, is connected to the negated input terminal, which has the negative polarity (−), of a differential amplifier <b>85</b>. The other I/V conversion circuit <b>32</b><i>a</i>, connected to the output terminal of the switch <b>88</b><i>b</i>, is connected to the non-negated input terminal, which has the positive polarity (+), of the differential amplifier <b>85</b>. The paired switches <b>88</b><i>a </i>and <b>88</b><i>b </i>are structured such that those reception conductors <b>12</b>, which are to be connected to the IN conversion circuits <b>32</b><i>a</i>, are changed over at predetermined time intervals. In particular, if it is assumed that the switch <b>88</b><i>a </i>is connected to the reception conductor X₀and the switch <b>88</b><i>b </i>is connected to the reception conductor X₁first, the switches <b>88</b><i>a </i>and <b>88</b><i>b </i>are changed over after a predetermined time interval such that the switch <b>88</b><i>a </i>is connected to the reception conductor X₁and the switch <b>88</b><i>b </i>is connected to the reception conductor X₂. Thereafter, the conductors to be connected are successively changed over at predetermined time intervals. Then, after the switch <b>88</b><i>a </i>is connected to the reception conductor X₇and the switch <b>88</b><i>b </i>is connected to the reception conductor X₈, the switches <b>88</b><i>a </i>and <b>88</b><i>b </i>are changed over such that the switch <b>88</b><i>a </i>is again connected to the reception conductor X₀and the switch <b>88</b><i>b </i>is again connected to the reception conductor X₁.

p-0221Where the differential amplifier <b>85</b> is used in the reception section, since noise included in outputs from the reception conductors <b>12</b> is canceled by the differential amplifiers <b>85</b>, the noise resisting property can be improved.

p-0222[Modification 7]

p-0223While in modification 6 the number of reception conductors to be connected to a differential amplifier is two, the number of reception conductors to be connected to a differential amplifier may be further increased. An example is shown in <figref idrefs="DRAWINGS">FIG. 22</figref>.

p-0224<figref idrefs="DRAWINGS">FIG. 22</figref> shows a general configuration of a differential amplifier according to modification 7.

p-0225Referring to <figref idrefs="DRAWINGS">FIG. 22</figref>, in the differential amplifier <b>86</b> in modification 7, the number of reception conductors <b>12</b> connected at the same time to the differential amplifier <b>86</b> is five. Those five reception conductors <b>12</b>, which are positioned adjacent to each other, are used as the reception conductors <b>12</b> to be connected at the same time. In the example of <figref idrefs="DRAWINGS">FIG. 22</figref>, the five reception conductors <b>12</b> connected to the differential amplifier <b>86</b> shown are reception conductors X_m−2to X_m+2. In particular, the reception conductors X_m−2and X_m−1are connected to the negated input terminal of the differential amplifier <b>86</b>, and the reception conductors X_m+2and X_m+1are connected to the non-negated input terminal of the differential amplifier <b>86</b>. The central reception conductor X_mis connected to the terminal of a predetermined reference voltage level (e.g., ground) of the differential amplifier <b>86</b>. If the differential amplifier <b>86</b> is of the single power supply type, the voltage level of the reception conductor X_mis set to a predetermined reference voltage level, but if the differential amplifier <b>86</b> is of the double power supply type, the voltage level of the reception conductor X_mis zero.

p-0226Where a configuration as just described is adopted, a plurality of outputs from different reception conductors <b>12</b> are input at the same time to the differential amplifier <b>86</b>. As a result, since the level of the difference signal increases, the integration signal also increases, and the detection sensitivity can be improved. Further, since the number of reception conductors, whose output signals are to be input at the same time to the differential amplifier <b>86</b>, increases, the range over which detection is possible is expanded. Further, since the differential amplifier <b>86</b> is used, the noise resisting property can be improved similar to modification 6.

p-0227In the example of <figref idrefs="DRAWINGS">FIG. 22</figref>, the reception conductor selection circuit <b>31</b> is not shown. In the succeeding drawings, only those elements that are necessary for description of the present invention are shown. This applies also to illustration of the switches <b>22</b><i>a </i>of the transmission conductor selection circuit <b>22</b>.

p-0228The reason why the central reception conductor X_mto be connected to the differential amplifier <b>86</b> is set to the predetermined reference voltage level in modification 7 is as follows. In particular, as described above in connection with the first embodiment, in the electrostatic coupling system, current at a cross point near a pointer is shunted to the ground through the pointer, and the variation of the current at the cross point due to shunting is detected. However, if the pointer is not grounded sufficiently, then the shunting of current at the cross point becomes insufficient to be detected. In this instance, the current variation at the cross point becomes small, and the sensitivity in position detection decreases.

p-0229However, if the reception conductor which is positioned at the center of a plurality of reception conductors connected to the differential amplifier <b>86</b>, is set to a reference voltage level or the zero voltage as in modification 7, even if the pointer is not grounded sufficiently, as long as the pointer is positioned in proximity to the reception conductor X_m, part of the current can be shunted through both the pointer and the reception conductor X_m. As a result, the decrease in the sensitivity described above can be minimized.

p-0230[Modification 8]

p-0231While in modifications <b>6</b> and <b>7</b> a differential amplifier is utilized to assure high detection sensitivity, it is also possible to inverse the phase of a periodic signal, which is to be supplied to a transmission conductor, to assure high detection sensitivity.

p-0232<figref idrefs="DRAWINGS">FIG. 23</figref> illustrates a supplying form of a periodic signal in modification 8. Referring to <figref idrefs="DRAWINGS">FIG. 23</figref>, modification 8 is configured such that, between the multi-frequency signal supplying circuit <b>21</b> and the transmission conductor selection circuit <b>22</b> of the transmission section <b>20</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref>, a phase inversion circuit <b>87</b> for inversing the phase of a periodic signal produced by each periodic signal production section <b>24</b> is provided. When a periodic signal of a predetermined frequency f_kis supplied to a transmission conductor Y_n+1, the phase inversion circuit <b>87</b> inverses the phase of the periodic signal of the frequency f_kand supplies the periodic signal of the inversed phase to a transmission conductor Y_n. Then, in the reception section <b>30</b> shown <figref idrefs="DRAWINGS">FIG. 1</figref>, currents output from the two reception conductors X_n+1and X_npositioned adjacent to each other are input to a two-input one-output amplifier <b>90</b>. Both input terminals of the amplifier <b>90</b> are non-negated (+) terminals.

p-0233Where the phase inversion circuit <b>87</b> is used in the transmission section <b>20</b>, when a pointer is not positioned in proximity, signals output from the two reception conductors X_n+1and X_nto be used for detection simultaneously cancel each other and therefore, the detection sensitivity can be improved.

p-0234[Modification 9]

p-0235In modification 8 described above, in order to enhance the detection sensitivity, a periodic signal produced by the transmission section and an inverted phase signal having a phase inverse to that of the periodic signal are utilized and a two-input one-output amplifier is used in the reception section. However, in order to achieve enhancement of the detection sensitivity and expansion of the range for detection without using an inverted phase signal, a periodic signal having the same frequency may be supplied to a plurality of transmission conductors while a plural-input one-output amplifier is used in the reception section.

p-0236<figref idrefs="DRAWINGS">FIG. 24</figref> illustrates a supplying form of a periodic signal and a detection form of an output signal according to modification 9. Referring to <figref idrefs="DRAWINGS">FIG. 24</figref>, a two-input one-output amplifier <b>90</b> with two inputs being non-negated (+) terminals is used in the reception section <b>30</b>. Where the amplifier <b>90</b> is used, periodic signals of the same frequency are supplied to two transmission conductors <b>14</b>.

p-0237Where periodic signals of the same frequency are supplied to a plurality of transmission conductors <b>14</b> and output signals from a plurality of reception conductors <b>12</b> are added, not only the level of the output signal to be detected can be increased, but also the detection range can be expanded. Where output signals of a plurality of reception conductors are added, since the detection range can be expanded, the configuration described is suitable particularly where the position detection region of the sensor section <b>10</b> is large.

p-0238In modification 9 described above, periodic signals of the same frequency are supplied in a unit of two transmission conductors <b>14</b>, while output signals of two reception conductors <b>12</b> are added in the reception section. However, the number of transmission conductors <b>14</b>, to which periodic signals of the same frequency are to be supplied, may be three or more, and the number of reception conductors <b>12</b> whose outputs are to be added by an amplifier of the reception section may also be three or more accordingly.

p-0239Further, while in modification 9, the number of reception conductors <b>12</b> whose outputs are added by an amplifier is equal to the number of transmission conductors <b>14</b> to which periodic signals of the same frequency are supplied, the present invention is not limited to such arrangement. The number of transmission conductors <b>14</b> to which periodic signals of the same frequency are to be supplied and the number of reception conductors <b>12</b> whose outputs are to be added by an amplifier may be different. Where the number of transmission conductors <b>14</b>, to which periodic signals of the same frequency are to be supplied and the number of reception conductors <b>12</b> whose outputs are to be added by an amplifier are set equal to each other, the following advantages can be achieved.

p-0240In particular, where the number of transmission conductors, to which periodic signals of the same frequency are to be transmitted, is different from the number of reception conductors <b>12</b>, whose outputs are to be added by an amplifier, the minimum detection region on the sensor section <b>10</b> has a rectangular shape, resulting in production of anisotropy in sensitivity distribution. In this instance, if the sensor section <b>10</b> detects a pointer whose face opposing the sensor section <b>10</b> has a circular shape (such face is hereinafter referred to as “opposing face”), the opposing face of the pointer is not detected as a circular shape but as a deformed shape, like an elliptic shape. On the other hand, where the number of transmission conductors, to which periodic signals of the same frequency are to be transmitted, is equal to the number of reception conductors <b>12</b>, whose outputs are to be added by an amplifier as in modification 9, the minimum detection region S_minon the sensor section <b>10</b> has a square shape, and an isotropic sensitivity distribution is obtained. In this instance, when a pointer with a circular opposing face is disposed on the sensor section <b>10</b>, the opposing face of the pointer can be detected as a circular shape.

p-0241In the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 5</figref>, rotation of a frequency is carried out in an example wherein each periodic signal to be supplied to the transmission conductors <b>14</b> in a transmission block <b>25</b> has a different frequency from each other. However, where periodic signals of the same frequency are supplied to each of two transmission conductors <b>14</b> positioned adjacent to each other, as in the case of modification 9, the frequency may be rotated after every predetermined period of time as described above. Different examples are illustrated in <figref idrefs="DRAWINGS">FIGS. 25A and 25B</figref> and <figref idrefs="DRAWINGS">FIGS. 26A to 26C</figref>.

p-0242In the example of rotation illustrated in <figref idrefs="DRAWINGS">FIGS. 25A and 25B</figref>, periodic signals of a frequency f₀having the same phase are supplied to the transmission conductors Y₂and Y₃first at a certain, time, as seen in <figref idrefs="DRAWINGS">FIG. 25A</figref>. Then, after a predetermined interval of time, periodic signals of the frequency f₀having the same phase are supplied to the transmission conductors Y₀and Y₁as seen in <figref idrefs="DRAWINGS">FIG. 25B</figref>. In short, in the example of rotation of <figref idrefs="DRAWINGS">FIGS. 25A and 25B</figref>, the transmission conductors <b>14</b>, to which periodic signals of the same frequency are to be supplied, are shifted or displaced in a unit of two transmission conductors after every predetermined interval of time.

p-0243Where the rotation wherein the transmission conductors <b>14</b>, to which periodic signals of the same frequency are to be supplied, are displaced in a unit of two transmission conductors in this manner, detection of a pointer can be carried out at a higher speed.

p-0244In the example of rotation illustrated in <figref idrefs="DRAWINGS">FIGS. 26A to 26C</figref>, periodic signals of the frequency f₀having the same phase are supplied to the transmission conductors Y₂and Y₃at a certain time as seen in <figref idrefs="DRAWINGS">FIG. 26A</figref>. After a predetermined interval of time, periodic signals of the frequency f₀having the same phase are supplied to the transmission conductors Y₁and Y₂, as seen in <figref idrefs="DRAWINGS">FIG. 26B</figref>. Then, after an equal predetermined interval of time elapses, periodic signals of the frequency f₀having the same phase are supplied to the transmission conductors Y₀and Y₁, as seen in <figref idrefs="DRAWINGS">FIG. 26C</figref>. In short, in the example of <figref idrefs="DRAWINGS">FIGS. 26A to 26C</figref>, the transmission conductors <b>14</b>, to which periodic signals of the same frequencies are to be supplied, are displaced by one transmission conductor after every predetermined interval of time.

p-0245With the rotation wherein the transmission conductors <b>14</b>, to which periodic signals of the same frequency are to be supplied, are displaced in a unit of one transmission conductor after every predetermined interval of time, since periodic signals of the same frequency are supplied to a plurality of transmission conductors <b>14</b>, the detection accuracy can be enhanced in comparison with the example according to the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 5</figref>.

p-0246[Modification 10]

p-0247In modification 9 described above, the number of reception conductors <b>12</b> whose outputs are to be added by an amplifier on the reception side is increased by two, three or more so that the level curve of the output signals becomes broader to expand the detection range. However, if the number of reception conductors is increased in the frequency multiplex system (particularly one that does not use a differential amplifier), there is a possibility that the level of the current flowing into the reception conductors by synthesis of the periodic signals may become much higher than the level suited for detection. As a result, the dynamic range of an amplifier or the like of the reception section <b>30</b> may be exceeded and the amplifier may become saturated. <figref idrefs="DRAWINGS">FIG. 27</figref> illustrates an example of a level curve detected in modification 9 shown in <figref idrefs="DRAWINGS">FIG. 24</figref>, wherein the level curve <b>90</b>X includes steep rising and falling edges and also indicates a high level. When the number of reception conductors <b>12</b> increases to three, four and so forth, the reception level further rises and the current flowing into the reception conductors increases by synthesis of periodic signals. Therefore, in modification 10, in order to suppress current flowing into reception conductors by synthesis of periodic signals while broadening the level curve of the output signal, a reception conductor connected to the ground is provided between the other reception conductors. An example is shown in <figref idrefs="DRAWINGS">FIG. 28</figref>.

p-0248<figref idrefs="DRAWINGS">FIG. 28</figref> illustrates a supplying form of periodic signals and a detection form of an output signal in modification 10. Referring to <figref idrefs="DRAWINGS">FIG. 28</figref>, in modification 10, a three-input one-output amplifier <b>91</b> having threes input terminals is used. The three input terminals are formed such that the opposite side ones thereof are non-negated (+) terminals while the central one thereof is connected to the ground. The central input terminal is hereinafter referred to as “0” terminal. The input terminals of the amplifier <b>91</b> are connected to the reception conductor selection circuit <b>31</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref>. In particular, reception conductors X_mand X_m+2positioned on the opposite sides of arbitrary three reception conductors X_mto X_m+2of the reception conductor selection circuit <b>31</b>, which are positioned adjacent to each other, are connected to the non-negated terminals on the opposite sides of the amplifier <b>91</b>. The reception conductor X_m+1of the reception conductor selection circuit <b>31</b> that is positioned centrally is connected to the “0” terminal of the amplifier <b>91</b>. In other words, the level of an output signal from the central reception conductor X_m+1is zero.

p-0249In the configuration just described, the output signal output from the amplifier <b>91</b> in modification 10 exhibits a level curve <b>91</b>X illustrated in <figref idrefs="DRAWINGS">FIG. 28</figref>. In particular, as seen in <figref idrefs="DRAWINGS">FIG. 28</figref>, the level curve <b>91</b>X has a broad curved shape having a magnitude equal to or smaller than that of the “++” reception by two reception conductors, while having a breadth substantially equal to that of the “+++” reception by three reception conductors. In modification 10, as the curved shape of the level curve <b>91</b>X becomes broader, the maximum value thereof is suppressed to a value lower than that where three reception conductors are involved. The value may also be lower than that where two reception conductors are involved. The detection range is substantially the same as that where three reception conductors are involved. Further, connecting one of the reception conductors to the ground plays a role similar to that where a pointer is connected to the ground.

p-0250Since the output signal from the reception conductor X_m+1connected to the ground is zero, the central one of three transmission conductors may be connected to the ground in accordance with the connection condition of the reception conductors. Where the configuration just described is used, it contributes not only to improvement of the level curve of an output signal to be detected, but also to suppression of power consumption. Further, since small swells are generated by multiplexing of periodic signals even if a differential amplifier is used, the transmission side may use a connection scheme which exhibits a similar signal level in a corresponding relationship to the connection scheme of the reception side.

p-0251Where a reception conductor to be connected to the ground is provided between other reception conductors as described above, the shape of the level curve can be made broad while swells of the level curve remain suppressed. Therefore, output signals can be detected at the same time through a plurality of reception conductors while the level of the level curve is suppressed, and the coordinate recognition characteristic is improved. Further, the detection range can be expanded to a plurality of reception conductors while suppressing the level of the level curve.

p-0252<figref idrefs="DRAWINGS">FIG. 29</figref> illustrates another supplying form of periodic signals and another detection form of an output signal in modification 10. Referring to <figref idrefs="DRAWINGS">FIG. 29</figref>, in the example of modification 10, a four-input one-output amplifier <b>92</b> having four input terminals is used. The four input terminals of the amplifier <b>92</b> include non-negated (+) terminals and “0” terminals arranged alternately. The “0” terminals are connected to the ground. The input terminals are connected to the reception conductor selection circuit <b>31</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref>. In particular, arbitrary four reception conductors X_mto X_m+3of the reception conductor selection circuit <b>31</b>, which are positioned adjacent to each other, are respectively connected to the non-negated terminals and the negated terminals of the amplifier <b>92</b>. In particular, of the four adjacent reception conductors X_mto X_m+3, the reception conductors X_m+1and X_m+3are connected to the ground so that the level of the output signals from the reception conductors X_m+1and X_m+3is set to zero. Alternate ones of the transmission conductors Y_nto Y_n+3, that is, the transmission conductors Y_nand Y_n+2, may be connected to the ground in a corresponding relationship to the connection scheme of the reception conductors, as seen in <figref idrefs="DRAWINGS">FIG. 29</figref>. Further, another configuration is possible wherein the reception conductors X_m−1and X_m+1are connected to the “0” terminals while the reception conductors X_mand X_m+2are connected to the non-negated terminals.

p-0253In this example, for example, if a four-input one-output amplifier is used and all of the input terminals of the same are non-negated terminals, that is, if four arbitrary reception conductors selected by the reception conductor selection circuit <b>31</b> are used to carry out “++++” reception, the level curve of the output signal will exceed the dynamic range of the amplifier <b>92</b> due to swells and so forth based on synthesis of periodic signals, resulting in saturation of the amplifier <b>92</b>. However, where “+0+0” or “0+0+” reception is carried out (alternate ones of the reception conductors are connected to the ground), although an equal number of reception conductors are used, the level curve of the output signal is not saturated.

p-0254According to the example of modification 10 described above with reference to <figref idrefs="DRAWINGS">FIG. 29</figref>, a plurality of periodic signals of the same frequency are supplied to the corresponding transmission conductors <b>14</b> and output signals from alternate ones of the reception conductors <b>12</b> are added similarly as in the example described above with reference to <figref idrefs="DRAWINGS">FIG. 28</figref>. In the configuration described, the detection range can be expanded while current flowing into the reception conductors is suppressed to a suitable degree, and the level of the output signal to be detected can be increased. Therefore, the detection sensitivity can be enhanced. Further, the example of modification 10 described above with reference to <figref idrefs="DRAWINGS">FIG. 29</figref> is suitable particularly where the position detection region on the sensor section <b>10</b> is great since the detection range can be expanded and the level of the output signal to be detected can be increased similar to the example of <figref idrefs="DRAWINGS">FIG. 28</figref>.

p-0255In modification 10 illustrated in <figref idrefs="DRAWINGS">FIGS. 28 and 29</figref>, the supplying pattern of periodic signals of the same frequency to the transmission conductors <b>14</b> is the same as the connection pattern of the reception conductors <b>12</b> whose outputs are to be added by an amplifier. In this instance, the minimum detection region on the sensor section <b>10</b> becomes a square shape, and an isotropic distribution is obtained.

p-0256[Modification 11]

p-0257As an example for improving the noise resisting property of an output signal to be detected by the reception section <b>30</b>, a configuration which uses a differential amplifier to carry out differential driving is available. An example of a supplying form of periodic signals and a detection form of an output signal where four reception conductors form a detection range is illustrated in <figref idrefs="DRAWINGS">FIG. 30</figref>. <figref idrefs="DRAWINGS">FIG. 30</figref> illustrates modification 11, which uses a four-input one-output differential amplifier <b>93</b>. The four input terminals of the differential amplifier <b>93</b> include negated (−) terminals and non-negated (+) terminals disposed such that the terminals of the same polarity are disposed in a neighboring relationship with each other. Thus, the reception conductors X_mand X_m+1from arbitrary four reception conductors X_mto X_m+3of the reception conductor selection circuit <b>31</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref> are connected to the non-negated terminals of the differential amplifier <b>93</b>, while the reception conductors X_m+2and X_m+3are connected to the negated terminals of the differential amplifier <b>93</b>.

p-0258Where the signal detection form of the reception section is “++−−” as in modification 11, the signal supplying form of the transmission section is preferably set in conformity with the signal detection form. In particular, periodic signals having “negative, negative, positive, positive” phases in the ascending order of the indexes of the transmission conductors <b>14</b> are supplied to the four transmission conductors Y_nto Y_n+3positioned adjacent to each other. In order to implement this, periodic signals of a frequency f_kare supplied to the transmission conductors Y_n+2to Y_n+3without changing the phase thereof, as seen in <figref idrefs="DRAWINGS">FIG. 30</figref>. Meanwhile, periodic signals of the frequency f_kare supplied through phase inversion circuits <b>87</b> to the transmission conductors Y_nto Y_m+1.

p-0259In this example, a level curve <b>93</b>X illustrated in <figref idrefs="DRAWINGS">FIG. 30</figref> represents the level or output value of the output signal originating from the four reception conductors <b>12</b>. Where the differential amplifier <b>93</b> with the configuration described above is used in the reception section, noise included in a synthetic signal of the reception conductors X_mand X_m+1and a synthetic signal of the reception conductors X_m+2and X_m+3cancel each other in the differential amplifier <b>93</b>. Therefore, the noise resisting property can be enhanced.

p-0260Where a differential amplifier is used, the level variation of the output signal obtained when a pointer actually touches the sensor section exhibits an S-shaped characteristic, as indicated by a broken line in <figref idrefs="DRAWINGS">FIG. 30</figref>. In order to calculate the position of the pointer, the output signal must have one peak value, as in the level curve <b>93</b>X. This is because a reception conductor, which exhibits the peak value, indicates the position at which the pointer actually touches. Such an output signal, which has one peak value as just described, can be obtained by applying an integration process to an output signal having an S-shaped characteristic indicated by a broken line in <figref idrefs="DRAWINGS">FIG. 30</figref>. However, the integration process accumulates noise, and the position detection accuracy may thus deteriorate.

p-0261Therefore, in modification 11, the same number of input terminals of different polarities can be arranged in the left and right portions of a differential amplifier of the reception section <b>30</b> such that left and right output signals to be detected are balanced. An example is shown in <figref idrefs="DRAWINGS">FIG. 31</figref>.

p-0262<figref idrefs="DRAWINGS">FIG. 31</figref> illustrates an example of a supplying form of periodic signals and a detection form of an output signal where the detection range includes four reception conductors. Referring to <figref idrefs="DRAWINGS">FIG. 31</figref>, in the example shown, a four-input one-output differential amplifier <b>94</b> is used. The four input terminals of the differential amplifier <b>94</b> are disposed such that the non-negated (+) terminals and the negated (−) terminals are symmetrical with each other in the leftward and rightward direction. The reception conductor selection circuit <b>31</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref> is connected to the differential amplifier <b>94</b> such that arbitrary four reception conductors X_mto X_m+3positioned adjacent to each other are connected to the four input terminals of the differential amplifier <b>94</b>. In particular, of the four adjacent reception conductors X_mto X_m+3, the reception conductors X_m+1and X_m+2are connected to the non-negated terminals of the differential amplifier <b>94</b> and the reception conductors X_mand X_m+3are connected to the negated terminals. In the transmission section <b>20</b>, it is preferable to arrange the supplying pattern of periodic signals to match the polarities of the input terminals of the differential amplifier <b>94</b> to which the reception conductors <b>12</b> are connected. Specifically, of arbitrary four transmission conductors Y_nto Y_n+3positioned adjacent to each other and selected by the transmission conductor selection circuit <b>22</b>, periodic signals of the frequency f_kare supplied to the transmission conductors Y_n+1to Y_n+2, while, to the transmission conductors Y_nto Y_n+3, periodic signals having a phase reversed from that of the periodic signals of the frequency f_kare supplied through the phase inversion circuit <b>87</b>.

p-0263An output signal obtained from the differential amplifier <b>94</b> in modification 11 has one peak value as seen from a level curve <b>94</b>X illustrated in <figref idrefs="DRAWINGS">FIG. 31</figref>. As a result, since the necessity for an integration process of an output signal of the differential amplifier is eliminated, the noise resisting property can be improved. Therefore, a signal when the sensor section is pointed by a pointer can be detected with certainty.

p-0264While in modification 11 described above, the number of reception conductors to be connected to a differential amplifier is four, the number of reception conductors is not limited to four or any even number. It may also be a unit of an odd number, such as three or five. Further, the phase reversal may be carried out not only on the reception conductors side, but also on the transmission conductors side or on both of the reception conductors side and the transmission conductors side. Further, the central reception conductor may be connected to the ground or to an arbitrary reference potential as in the example of <figref idrefs="DRAWINGS">FIG. 28</figref>.

p-0265Further, while the disposition of the input terminals of the differential amplifier in modification 11 described above is “−++−,” the disposition of the input terminals is not limited to this example, and it is only necessary for the input terminals to be disposed symmetrically in the leftward and rightward direction. Thus, <figref idrefs="DRAWINGS">FIG. 32</figref> illustrates a different example of a supplying form of periodic signals and a detection form of an output signal where the detection range includes four reception conductors.

p-0266Referring to <figref idrefs="DRAWINGS">FIG. 32</figref>, a four-input one-output differential amplifier <b>95</b> is used, and the input terminals of the differential amplifier <b>95</b> are disposed such that non-negated (+) terminals and negated (−) terminals are switched relative to those used in modification 11 described above with reference to <figref idrefs="DRAWINGS">FIG. 31</figref>. The reception conductor selection circuit <b>31</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref> is connected to the differential amplifier <b>95</b> such that arbitrary four reception conductors X_mto X_m+3positioned adjacent to each other of the reception conductor selection circuit <b>31</b> are connected to the four input terminals of the differential amplifier <b>95</b>. In particular, from the four adjacent reception conductors X_mto X_m+3, the reception conductors X_mand X_m+3are connected to the non-negated terminals of the differential amplifier <b>95</b>, while the reception conductors X_m+1and X_m+2are connected to the negated terminals of the differential amplifier <b>95</b>. In the transmission section <b>20</b>, of arbitrary four transmission conductors Y_nto Y_n+4positioned adjacent to each other and selected by the transmission conductor selection circuit <b>22</b>, to the transmission conductors Y_nand Y_n+3periodic signals of the frequency f_kare supplied. To the transmission conductors Y_n+1and Y_n+2, periodic signals having a phase reversed from that of the periodic signals of the frequency f_kare supplied through the phase inversion circuit <b>87</b>. As a result, the supplying pattern of periodic signals corresponds to the polarities of the input terminals of the differential amplifier <b>95</b>, to which the reception conductors <b>12</b> are connected. In other words, in the example of <figref idrefs="DRAWINGS">FIG. 32</figref>, the disposition of the input terminals of the differential amplifier <b>95</b> is “+−−+.” In the case of “+−−+” also, the necessity for an integration process of an output signal of the differential amplifier is eliminated similar to the example described above with reference to <figref idrefs="DRAWINGS">FIG. 31</figref>. Consequently, the noise resisting property can be improved.

p-0267[Modification 12]

p-0268While, in modification 11 described above, the detection range includes four reception conductors, in modification 12, the detection range includes three reception conductors.

p-0269<figref idrefs="DRAWINGS">FIG. 33A</figref> illustrates a supplying form of periodic signals and a detection form of an output signal where the detection range includes three reception conductors, as modification 12, and <figref idrefs="DRAWINGS">FIG. 33B</figref> illustrates an example different from modification 12 of <figref idrefs="DRAWINGS">FIG. 33A</figref>.

p-0270In the example of <figref idrefs="DRAWINGS">FIG. 33A</figref>, a three-input one-output differential amplifier <b>96</b> is used. The three input terminals of the differential amplifier <b>96</b> are disposed such that the non-negated (+) terminal and the negated (−) terminals are symmetrical with each other in the leftward and rightward direction. Then, the reception conductor selection circuit <b>31</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref> is connected to the differential amplifier <b>96</b> such that arbitrary three reception conductors X_mto X_m+2of the reception conductor selection circuit <b>31</b> positioned adjacent to each other are connected to the three input terminals of the differential amplifier <b>96</b>. More particularly, of the three reception conductors X_mto X_m+2positioned adjacent to each other, the reception conductor X_m+1is connected to the non-negated terminal, and the reception conductors X_mand X_m+2are connected to the negated terminal. Meanwhile, in the transmission section <b>20</b>, to the transmission conductor Y_n+1from among arbitrary three transmission conductors Y_nto Y_n+2positioned adjacent to each other and selected by the transmission conductor selection circuit <b>22</b>, periodic signals of the frequency f_kare supplied. To the transmission conductors Y_nand Y_n+2, periodic signals having a phase reversed from that of the periodic signals of the frequency f_kare supplied through the phase inversion circuit <b>87</b>. As a result, the supplying pattern of periodic signals corresponds to the polarities of the input terminals of the differential amplifier <b>96</b> to which the reception conductors <b>12</b> are connected.

p-0271In the example of <figref idrefs="DRAWINGS">FIG. 33B</figref>, the polarities of the input terminals of the differential amplifier of <figref idrefs="DRAWINGS">FIG. 33A</figref> are reversed. In particular, a three-input one-output differential amplifier <b>97</b> is used. The three input terminals of the differential amplifier <b>97</b> are disposed such that the non-negated (+) terminals and the negated (−) terminal are symmetrical with each other in the leftward and rightward direction. Then, the reception conductor selection circuit <b>31</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref> is connected to the differential amplifier <b>97</b> such that arbitrary three reception conductors X_mto X_m+2of the reception conductor selection circuit <b>31</b> positioned adjacent to each other are connected to the three input terminals of the differential amplifier <b>97</b>. More particularly, of the three reception conductors X_mto X_m+2positioned adjacent to each other, the reception conductors X_mand X_m+2are connected to the non-negated terminal and the reception conductor X_m+1is connected to the negated terminal Meanwhile, in the transmission section <b>20</b>, to the transmission conductors Y_mand Y_m+2from among arbitrary three transmission conductors Y_mto Y_m+2positioned adjacent to each other and selected by the transmission conductor selection circuit <b>22</b>, periodic signals of the frequency f_kare supplied. To the transmission conductor Y_m+1, a periodic signal having a phase reversed from that of the periodic signals of the frequency f_kis supplied through the phase inversion circuit <b>87</b>. As a result, the supplying pattern of period signals corresponds to the polarities of the input terminals of the differential amplifier <b>97</b> to which the reception conductors <b>12</b> are connected.

p-0272In the examples illustrated in <figref idrefs="DRAWINGS">FIGS. 33A and 33B</figref>, in order to establish a balanced state between output signals obtained at the input terminals of different polarities, an output signal obtained from a terminal of one polarity, to which a comparatively smaller number of reception conductors are connected, and output signals obtained at terminals of the other polarity, to which a comparatively greater number of reception conductors are connected, are balanced with each other. In particular, the level of an output signal obtained at the “+(−)” terminal of the differential amplifier <b>96</b> (<b>97</b>) is increased to twofold, and both this output signal increased to twofold and output signals obtained at the other two “−(+)” terminals are used. In this example, to what extent (i.e., to what number of times) the level of the output signal obtained at an input terminal or terminals of a polarity for which the number of terminals provided is comparatively small is to be increased, is determined based on both the number of input terminals of the polarity with which the number of reception terminals connected is comparatively small and the number of input terminals of the other polarity with which the number of reception terminals connected is comparatively great.

p-0273With modification 12, even where the number of conductors to be detected is a unit of an odd number, left and right output signals detected upon detection waiting can be balanced with each other similar to the examples of modification 11 illustrated in <figref idrefs="DRAWINGS">FIGS. 31 and 32</figref>. Further, with modification 12, the minimum detection region S_mincan be reduced in comparison with that in modification 11 in addition to the effect that the noise resisting property is improved similarly to modification 11.

p-0274[Modification 13]

p-0275Modification 13 is modification to the first embodiment in that a nonlinear process is carried out for a level curve or level characteristic of an output signal obtained when a pointer actually touches the sensor section. Modification 13 is described with reference to <figref idrefs="DRAWINGS">FIGS. 34 and 35</figref>.

p-0276<figref idrefs="DRAWINGS">FIG. 34</figref> illustrates a signal level upon ordinary detection of a finger. Usually, a level curve <b>101</b> of an output signal obtained by the reception section <b>30</b> when a pointer such as a finger <b>19</b> touches the detection surface of the sensor section <b>10</b> has such a characteristic as seen in <figref idrefs="DRAWINGS">FIG. 34</figref>. The level of the output signal obtained upon touching by the pointer is very high at the touched location of the sensor section <b>10</b>. On the other hand, the level of the output signal is very low at a portion of the sensor section <b>10</b> at which the pointer is spaced from the sensor section <b>10</b>, that is, at a non-touched portion of the sensor section <b>10</b>. Even if a recognition process is carried out at a location where the pointer is spaced a little from the sensor section <b>10</b>, the level of the output signal is very different between the two cases (the touched vs. non-touched) and, therefore, an accurate recognition process is difficult.

p-0277Thus, in modification 13, an output signal obtained upon touching by a pointer is subjected to a detection process by the signal detection circuit <b>34</b>, and then to logarithmic transformation. Where nonlinear transformation such as logarithmic transformation is carried out, a signal portion of the output signal, which has a comparatively low level and corresponds to a non-touched portion of the sensor section <b>10</b>, can be made to stand out while the signal level of another signal portion, which has a comparatively high level and corresponds to a touched portion of the sensor section <b>10</b>, can be suppressed.

p-0278<figref idrefs="DRAWINGS">FIG. 35</figref> illustrates an example of a level curve after the nonlinear process of the output signal represented by the level curve <b>101</b> in the example of <figref idrefs="DRAWINGS">FIG. 34</figref>. The level curve <b>102</b> in the example of <figref idrefs="DRAWINGS">FIG. 35</figref> has a suppressed maximum value and is broadened. Therefore, the level of the output signal continues between adjacent reception conductors at the boundary between a touched portion and a non-touched portion of the sensor section <b>10</b> by the pointer. Consequently, a boundary recognition process for the pointer can be readily carried out. It is to be noted that a nonlinear process for the output signal is not limited to the logarithmic transformation and other suitable processes may be used.

p-0279According to the example described, an output signal obtained upon touching by a pointer is nonlinearly transformed once. Consequently, an output signal continues between adjacent reception conductors at the boundary between a touched portion and a non-touched portion of the sensor section <b>10</b>. Therefore, a boundary recognition process for the pointer can be readily carried out. Accordingly, a recognition characteristic with respect to a pointer can be improved. Such extraction of a surface area that is touched by the pointer including the boundary is important for the purpose of detecting a pointer coordinate, a pointer pressure, and so forth, as will be described later. Particularly when the pointer moves on the sensor section, a coordinate error that may otherwise occur when the pointer crosses over between reception conductors (i.e., a selection error of a reception conductor before and after such crossing over) can be reduced.

p-0280[Modification 14]

p-0281Modification 14 is an example in which identification of a state wherein a pointer is spaced away from the detection surface of the sensor section in the first embodiment is carried out satisfactorily. The state described is hereinafter referred to as hovering.

p-0282Identification of whether or not a pointer touches the sensor section is conventionally recognized based only on a gradient <b>102</b>A of an edge, that is, a rising edge, of a level curve of an output signal obtained from the reception conductors of the sensor section, as seen in <figref idrefs="DRAWINGS">FIG. 35</figref>. For example, when the gradient <b>102</b>A is steep, it is identified that a pointer <b>19</b> is touching the sensor section, but when the gradient <b>102</b>A is moderate, it is identified that a pointer is spaced away from the sensor section.

p-0283However, if a setting of the amplifier varies, accurate identification of a touching state becomes difficult. A method that identifies a hovering situation without being influenced by a detected level variation of the output signal is described below with reference to <figref idrefs="DRAWINGS">FIGS. 34 to 36</figref>.

p-0284In modification 14, a hovering situation is identified from a maximum value of the level curve of the output signal obtained from the reception conductors of the sensor section and a form of the level curve. The maximum value of the level curve is hereinafter referred to as a peak value. Therefore, the pointer detection apparatus of modification 14 includes ratio calculation means for detecting a peak value, which is the length of an arrow mark in <figref idrefs="DRAWINGS">FIG. 35</figref>, and the gradient <b>102</b>A of an edge of the level curve, and dividing the gradient <b>102</b>A of the edge by the peak value to determine a ratio. It further includes hovering identification means for identifying whether or not the pointer is in a hovering state depending upon whether or not the ratio is higher than a predetermined threshold value. In particular, the signal detection circuit <b>34</b> is provided with the ratio calculation means and the hovering identification means, and a result of the identification by the signal detection circuit <b>34</b> is transmitted to the position calculation circuit <b>35</b>. Alternatively, the functions of the ratio calculation means and the hovering identification means may be provided in the control circuit <b>40</b>.

p-0285The hovering identification means has stored therein a predetermined threshold value for deciding whether or not the pointer is in a hovering state, and has a function of comparing the ratio between the peak value and the gradient <b>102</b>A of the edge as determined by the ratio calculation means with the predetermined threshold value. If the ratio between the peak value and the gradient <b>102</b>A of the edge is higher than the predetermined threshold value, the hovering identification means decides that the pointer is in a non-hovering state, that is, the pointer is touching the sensor section. If the ratio between the peak value and the gradient <b>102</b>A of the edge calculated by the ratio calculation means is lower than the predetermined threshold value, the hovering identification means decides that the pointer is in a hovering state, that is, the pointer is not in touch with the sensor section. Further, the hovering identification means may set a second threshold value lower than the predetermined threshold value, and compare the second threshold value and the ratio between the peak value and the gradient <b>102</b>A of the edge determined by the ratio calculation means with each other. A degree of the hovering situation may thus be identified more particularly.

p-0286An example of determination of a peak value and a gradient of an edge is described with reference to <figref idrefs="DRAWINGS">FIG. 36</figref>. <figref idrefs="DRAWINGS">FIG. 36</figref> illustrates an example of normalized levels of output values of output signals detected by the reception section <b>30</b>. The present example represents a normalized value of the level of an output signal detected during a certain instantaneous time period, using three transmission conductors and three reception conductors. Since the level <b>100</b> as a maximum value is detected at the center and the level <b>50</b> is detected on the left and right sides of the center in the direction along a transmission conductor, the gradient of the edge in this instance is 100−50=50. Then, since the maximum value of the level curve of the output signal is 100, the value of the ratio to be determined is the gradient of edge/maximum value=50/100=0.5. In the example illustrated in <figref idrefs="DRAWINGS">FIG. 36</figref>, the peak value and the gradient of the edge of the output signal are determined from the level curve <b>102</b> illustrated in <figref idrefs="DRAWINGS">FIG. 35</figref> obtained by the non-linear process. They may otherwise be determined from the level curve <b>101</b> before the non-linear process.

p-0287According to the example illustrated in <figref idrefs="DRAWINGS">FIG. 36</figref>, since a hovering situation is identified based on a maximum value of the level curve of the detected output signal and a ratio of the shape of the level curve, stable identification of a hovering situation becomes possible. Therefore, the identification of a hovering situation is not influenced by the level variation of the output signal obtained from the reception conductors of the sensor section.

p-0288[Modification 15]

p-0289Modification 15 is an example suitable to carry out detection of hovering with certainty in the first embodiment.

p-0290Where hovering at a certain cross point or in a detection area is to be detected, if a predetermined number is selected as the number of transmission conductors and reception conductors which are to be rendered operative at the same time, then the number of conductors to be selected later is fixed. However, where this configuration is used, the detection sensitivity of hovering may become low as the influence of noise increases significantly. Therefore, reliable detection of hovering becomes difficult.

p-0291In modification 15, the number of transmission conductors and reception conductors to be rendered operative at the same time is dynamically varied. This operation is described with reference to <figref idrefs="DRAWINGS">FIGS. 37 and 38</figref>.

p-0292<figref idrefs="DRAWINGS">FIG. 37</figref> illustrates a supplying form of periodic signals and a detection form of an output signal where a pointer is positioned in proximity to the sensor section. <figref idrefs="DRAWINGS">FIG. 38</figref> illustrates a supplying form of periodic signals and a detection form of an output signal where a pointer is not positioned in proximity to the sensor section.

p-0293The example shown <figref idrefs="DRAWINGS">FIGS. 37 and 38</figref> has a configuration similar to that of modification 9 described above with reference to <figref idrefs="DRAWINGS">FIG. 24</figref>. In modification 15 of <figref idrefs="DRAWINGS">FIG. 37</figref>, a four-input one-output amplifier <b>98</b> whose four input terminals have the polarity of “+” is used in the reception section <b>30</b>.

p-0294In the example of <figref idrefs="DRAWINGS">FIG. 37</figref>, two transmission conductors <b>14</b>, which are positioned adjacent to each other, are selected to utilize two input terminals from among the four input terminals. In the transmission section <b>20</b>, periodic signals of the same frequency are preferably supplied to two adjacent ones of the transmission conductors <b>14</b>. Where a pointer is positioned in proximity to the sensor section, two transmission conductors <b>14</b> and two reception conductors <b>12</b> are selected to detect a current variation. Whether or not a pointer is positioned in proximity to the sensor section can be detected using modification 13 described above with reference to <figref idrefs="DRAWINGS">FIGS. 34 and 35</figref> or modification 14 described above with reference to <figref idrefs="DRAWINGS">FIGS. 35 and 36</figref>.

p-0295In the example illustrated in <figref idrefs="DRAWINGS">FIG. 38</figref>, the four-input one-output amplifier <b>98</b> is used in the reception section <b>30</b>, and the transmission section <b>20</b> selects four adjacent ones of the transmission conductors <b>14</b> to which periodic signals are to be supplied. Preferably, the periodic signals to be supplied from the transmission section <b>20</b> have the same frequency and are supplied to four transmission conductors <b>14</b> positioned adjacent to each other. In this manner, where a pointer is not positioned in proximity to the sensor section, four transmission conductors <b>14</b> and four reception conductors <b>12</b> are selected to increase the number of conductors to be used.

p-0296Such selection of the reception conductors <b>12</b> and the transmission conductors <b>14</b> is carried out by the control circuit <b>40</b>. The control circuit <b>40</b> receives an output from the position calculation circuit <b>35</b> to decide the distance between the sensor section and the pointer, and based on a result of the decision issues an instruction regarding a position and a number of conductors to be selected to both the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b>.

p-0297A particular example of hovering operation is described with reference to <figref idrefs="DRAWINGS">FIGS. 1</figref>, <b>37</b> and <b>38</b>.

p-0298It is assumed that two transmission conductors <b>14</b> and two reception conductors <b>12</b> are selected at a certain time to execute scanning, as seen in <figref idrefs="DRAWINGS">FIG. 37</figref>. The following description is given assuming that periodic signals having different frequencies from each other are supplied at the same time from the multi-frequency signal supplying circuit <b>21</b> to all transmission conductors <b>14</b>, which form the transmission conductor group <b>13</b>.

p-0299In this instance, the control circuit <b>40</b> first controls the reception conductor selection circuit <b>31</b> to select, for example, the reception conductors X_m+1and X_m+2. In this state, the reception section <b>30</b> carries out detection of a pointer using the selected reception conductors X_m+1and X_m+2. After the detection process by the reception section <b>30</b> is completed, the control circuit <b>40</b> controls the reception conductor selection circuit <b>31</b> to displace the reception conductors to select the reception conductors X_m+3and X_m+4, for example. Then, the reception section <b>30</b> carries out detection using the newly selected reception conductors X_m+3and X_m+4. Thereafter, selection of the reception conductors <b>12</b> and detection of a pointer as just described are repeated to carry out scanning of the entire sensor section <b>10</b>. Here, if the reception section <b>30</b> cannot detect a pointer, that is, if an output from the amplifier <b>98</b> is not detected, the control circuit <b>40</b> controls the reception conductor selection circuit <b>31</b> to increase the number of reception conductors <b>12</b> to be selected by the reception conductor selection circuit <b>31</b>, for example, to four, as seen in <figref idrefs="DRAWINGS">FIG. 38</figref>, and thereafter executes scanning.

p-0300Where the number of reception conductors <b>12</b> to be selected by the reception conductor selection circuit <b>31</b> is increased from two to four in this manner, since the number of output signals to be input from the reception conductors to the amplifier increases to four, the detection accuracy increases. Further, since the number of conductors to be selected increases from two to four, the time required for scanning the entire sensor section can be reduced, also.

p-0301While in modification 15 the number of conductors to be selected by the reception conductor selection circuit <b>31</b> is two or four, the number of conductors is not limited to four, but may be any number. Further, the number of reception conductors <b>12</b> to be selected at the same time is not limited to four. In other words, the control circuit <b>40</b> may control the reception conductor selection circuit <b>31</b> so that, as the distance between the sensor section and the pointer increases, the number of conductors to be selected by the reception conductor selection circuit <b>31</b> is gradually increased. Further, while, in the example of <figref idrefs="DRAWINGS">FIGS. 37 and 38</figref>, the amplifier described is of the type which carries out single (input) end operation, an amplifier of differential operation may be used instead. In modification 15, periodic signals having different frequencies from each other are supplied at the same time from the multi-frequency signal supplying circuit <b>21</b> to all transmission conductors <b>14</b> which form the transmission conductor group <b>13</b>. However, periodic signals to be supplied from the transmission section <b>20</b> may be changed over similarly, e.g., by gradually increasing the number of transmission conductors <b>14</b> that receive the same frequency signals.

p-0302In the present example, if it is decided that no pointer exists in proximity to the sensor section, the number of transmission conductors <b>14</b> and reception conductors <b>12</b> to be used is controlled so as to increase the detection sensitivity. Accordingly, reliable hovering detection can be implemented.

p-0303[Modification 16]

p-0304Modification 16 is an example suitable for advantageously carrying out all scanning desired to be carried out at a high speed with increased sensitivity. In particular, it is directed to roughly detecting a pointer in response to a signal level of a detection signal detected by the sensor section.

p-0305In the present description, “all scanning” means to sequentially carry out a detection process for a current variation (i.e., scanning) to cover all cross points on the sensor section in order to detect a pointer. It is desired that all scanning is carried out at a high speed with increased sensitivity. However, if all scanning of the transmission conductors and the reception conductors is carried out for each conductor or for each group of a small number of conductors, the sensitivity decreases, and since the number of scanning points is large, the time required for all scanning becomes long.

p-0306Therefore, in modification 16, if an output signal is not detected from the sensor section, the number of transmission conductors and reception conductors to be used for a single-time detection process is increased (as compared to that used in all scanning) to make rough scanning of scanning points (hereinafter referred to as “skip scanning”). In the skip scanning, the minimum detection region is made greater, and a detection process for a current variation is carried out using the minimum detection region as a minimum unit of displacement or shifting.

p-0307In order to implement the skip scanning, the signal detection circuit <b>34</b> is provided with a function of detecting presence or absence of an output signal. The signal detection circuit <b>34</b> transmits a result of the detection to the control circuit <b>40</b>. The control circuit <b>40</b> receives the result of detection from the signal detection circuit <b>34</b> and controls the number of conductors to be selected by the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b> based on the received detection result. If a pointer is not detected, that is, if an output signal is not detected, the control circuit <b>40</b> controls the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b> to increase the number of transmission conductors <b>14</b> and reception conductors <b>12</b> to be used for transmission and reception of signals. If a pointer is detected, that is, if an output signal is detected, the control circuit <b>40</b> controls the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b> to decrease the number of transmission conductors <b>14</b> and reception conductors <b>12</b> to be selected by the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b>, respectively.

p-0308A particular example of the skip scanning is described with reference to <figref idrefs="DRAWINGS">FIGS. 1 and 38</figref>.

p-0309If all scanning is carried out but an output signal is not detected, the control circuit <b>40</b> controls the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b> so that four conductors, that is, four transmission conductors Y_nto Y_n+3and four reception conductors X_mto X_m+3, may be selected from the transmission conductors <b>14</b> and the reception conductors <b>12</b> to initiate skip scanning. Then, after scanning is carried out for the selected four reception conductors X_mto X_m+3, the control circuit <b>40</b> controls the reception conductor selection circuit <b>31</b> to shift the reception conductors to be selected to carry out scanning of the reception conductors X_m+4to X_m+7(not shown). Thereafter, the control circuit <b>40</b> repeats selection and scanning of the transmission conductors <b>14</b> and the reception conductors <b>12</b>, and changeover of the transmission conductors <b>14</b> and the reception conductors <b>12</b> to be selected by the transmission conductor selection circuit <b>22</b> and the reception conductor selection circuit <b>31</b>, to repeat the operation for the entire sensor section <b>10</b>. Then, if a pointer is detected at any step, the control circuit <b>40</b> stops the skip scanning and executes all scanning using a smaller group of transmission conductors <b>14</b> and reception conductors <b>12</b> to be selected.

p-0310Where the number of reception conductors to be selected at the same time is changed to four as in the skip scanning of the present example, the sensitivity is increased. Further, since the detection position is shifted by a greater amount, in addition to the increased sensitivity, the detection time required for the entire sensor section is reduced. While in the example described the number of conductors to be selected at the same time during skip scanning is four, it is not limited to this particular number. The number of conductors to be selected during skip scanning may be any arbitrary number greater than that used in all scanning, for example, two, three or five. Further, while the number of reception conductors to be changed over (i.e., switched or shifted) is four, the number of reception conductors to be changed over is not limited to this number. For example, where four reception conductors are to be selected, they can be shifted by two, three or four conductors. In particular, in the description above using displacement by four conductors, reception is carried out using the reception conductors X_mto X_m+3first, and then the reception conductors to be selected are changed over to the reception conductors X_m+4to X_m+7, and so forth. However, displacement by two conductors is possible, wherein reception is carried out first using the reception conductors X_mto X_m+3, and then the reception conductors to be selected are changed over to the reception conductors X_m+2to X_m+5, and so forth. Further, while both of the transmission conductors and the reception conductors are selected four by four, the number of the transmission conductors may be different than the number of the reception conductors to be selected.

p-0311Further, while it is described that both the number of transmission conductors and the number of reception conductors to be selected are increased or decreased at the same time based on the level of the output signal, other arrangements are possible. For example, only the number of transmission conductors or the number of reception conductors may be increased or decreased. Various methods can be applied as long as the effective area, that is, the minimum detection region within which an output signal can be detected, is increased or decreased.

p-0312The number of transmission conductors and reception conductors to be used may be changed depending not only upon detecting the presence or absence of an output signal but also upon the degree of the level of the output signal. For example, when the level of the output signal is higher than a predetermined threshold value set in advance, the number of conductors is decreased, but when the level of the output signal is lower than the predetermined threshold value, the number of conductors is increased. Further, not one threshold value but a plurality of threshold values may be set. As a method of detecting the level of the output signal, the method of modification 13 described above with reference to <figref idrefs="DRAWINGS">FIGS. 34 and 35</figref>, modification 14 described above with reference to <figref idrefs="DRAWINGS">FIGS. 35 and 36</figref> or the like may be used.

p-0313In the present example, when a pointer is not detected, the number of transmission conductors and reception conductors to be selected at the same time is increased to carry out rough scanning of scan points, that is, to initiate skip scanning. Where the number of conductors is set in this manner, the detection sensitivity can be improved and high speed scanning can be implemented. Therefore, if modification 16 is applied to the first embodiment, that is, to the frequency multiplexing method, the time required for one cycle of scanning the entire sensor section <b>10</b> can be reduced significantly in comparison with the conventional systems because of a synergistic effect with the frequency multiplexing.

p-0314[Modification 17]

p-0315Modification 17 is suitable to more accurately detect a touched location of the sensor section by a pointer or detect a pointer positioned in proximity to the sensor section in the first embodiment.

p-0316As described in connection with the first embodiment illustrated in <figref idrefs="DRAWINGS">FIG. 2</figref> and modification 1 illustrated in <figref idrefs="DRAWINGS">FIG. 14</figref> as well as modification 2 illustrated in <figref idrefs="DRAWINGS">FIG. 15</figref>, the sensor section may have the transmission conductors and the reception conductors disposed with a spacer interposed therebetween, in two layers with a glass substrate interposed therebetween, or disposed in the same layer. Generally, in a structure which uses a spacer or a glass substrate, that is, in the structure wherein the distance between the detection surface and the transmission conductors is different than the distance between the detection surface and the reception conductors, the intensities of an electric field acting between the detection surface and the transmission and reception conductors are different. Therefore, the level curve of an output signal from a conductor spaced away from the detection surface of the sensor section exhibits a broad shape while the level curve of an output signal from a conductor in proximity to the detection surface of the sensor section exhibits a sharp shape. In other words, the gradient of an edge of the level of an output signal from a conductor spaced away from the detection surface is moderate, while the gradient of an edge of the level curve of an output signal from a conductor in proximity to the detection surface is steep.

p-0317<figref idrefs="DRAWINGS">FIG. 39</figref> illustrates a supplying form of periodic signals and a detection form of an output signal where the number of transmission conductors and reception conductors is five. In the example of <figref idrefs="DRAWINGS">FIG. 39</figref>, a five-input one-output differential amplifier <b>99</b> is used. The five input terminals of the differential amplifier <b>99</b> include a “0” terminal at the center thereof and two non-negated (+) terminals and two negated (−) terminals disposed on the opposite sides of the “0” terminal Five reception conductors X_mto X_m+4positioned adjacent to each other are connected to the input terminals. In particular, of the five reception conductors X_mto X_m+4positioned adjacent to each other, the reception conductors X_mand X_m+1are connected to the negated terminals, the reception conductor X_m+2is connected to the “0” terminal, and the reception conductors X_m+3and X_m+4are connected to the non-negated terminals. Meanwhile, five transmission conductors <b>14</b> are connected so as to correspond in polarity to the input terminals of the differential amplifier <b>99</b>, to which the reception conductors <b>12</b> are connected. In particular, the central transmission conductor Y_n+2is grounded, and periodic signals of the frequency f_kare supplied to the two transmission conductors Y_nand Y_n+1, while periodic signals having a phase reversed from that of the periodic signals supplied to the transmission conductors Y_nto Y_n+1are supplied to the two transmission conductors Y_n+3to Y_n+4.

p-0318Where the structure of the sensor section in <figref idrefs="DRAWINGS">FIG. 39</figref> is the same as that of the sensor section <b>50</b> of modification 1 described above with reference to <figref idrefs="DRAWINGS">FIG. 14</figref>, because the reception conductors <b>12</b> are disposed at a position nearer to the detection surface than the transmission conductors <b>14</b>, the level curve of the output signals of the transmission conductors <b>14</b> becomes a broad curve. The level curve of the output signals of the reception conductors <b>12</b> becomes a sharp curve. Because a difference appears between the shapes of the level curves where they are viewed from the reception side and from the transmission side, even if the pointer has a round shape, there is the possibility that it may be detected as an elliptic shape, as indicated by a broken line in <figref idrefs="DRAWINGS">FIG. 39</figref>.

p-0319Therefore, in modification 17, the pointer detection apparatus is configured such that the detection width on those conductors which are disposed remotely from the detection surface of the sensor section is narrow, while the detection width on those conductors which are disposed nearer to the detection surface of the sensor section is wide. No difference may appear between the shapes or detection widths of the level curves of the output signals on the reception side and the transmission side.

p-0320<figref idrefs="DRAWINGS">FIG. 40</figref> illustrates a supplying form of periodic signals and a detection form of an output signal by modification 17. Referring to <figref idrefs="DRAWINGS">FIG. 40</figref>, the sensor section has the same structure as that of the sensor section <b>50</b> of modification 1, similar to the example described above with reference to <figref idrefs="DRAWINGS">FIG. 39</figref>, and uses the same differential amplifier <b>99</b>. The example of <figref idrefs="DRAWINGS">FIG. 40</figref> is different from the example of <figref idrefs="DRAWINGS">FIG. 39</figref> in that three transmission conductors <b>14</b> are selected so that periodic signals are supplied thereto, wherein the central transmission conductor Y_n+2from the three selected transmission conductors <b>14</b> is grounded, and a periodic signal is supplied to the transmission conductor Y_n+1and to the transmission conductor Y_n+3after the phase thereof is reversed by a phase inversion circuit <b>87</b>.

p-0321In the above configuration, if the level curve of the output signals is represented by a three-dimensional representation, and the shape of the level curve is cut away with a certain threshold value, the shapes or detection widths of the level curve portions of the output signals on the transmission side and the reception side are substantially the same. Therefore, no difference appears in the detection widths. As a result, the shape to be detected becomes a substantially round shape as indicated by a broken line in <figref idrefs="DRAWINGS">FIG. 40</figref>. In other words, the aperture ratios or aspect ratios on the transmission side and the reception side can be adjusted.

p-0322In modification 17, the sensor section is used wherein transmission conductors and reception conductors both having a substantially linear shape are juxtaposed, However, in place of the transmission conductors and the reception conductors having a linear shape, conductors having a land portion having a width greater than that of the conductor portions as in the case of modification 3 described above may be used. Further, the transmission conductors and the reception conductors may be formed with an arbitrary width. Also regarding the disposition pattern of the transmission conductors and the reception conductors, they may be formed in a juxtaposed concentric relationship with each other as in the case of modification 5, and also regarding the pitch between the conductors, it may be changed to an arbitrary pitch. Further, not only a differential amplifier but also an amplifier of a single (input) end configuration may be used.

p-0323In the present example, the pointer detection apparatus is configured such that the detection width of the conductors spaced far away from the detection face of the sensor section is comparatively narrow while the detection width of the conductors positioned in proximity to the detection face of the sensor section is comparatively broad. Therefore, no difference may appear between the shapes or detection widths of the level curves of the output signals on the reception side and the transmission side, and the aperture ratio or aspect ratio can be made close to 1. In other words, the shape of a portion of a pointer at which the pointer touches the detection surface can be recognized with a higher degree of accuracy. For example, a round shape can be detected as a round shape without being deformed to an elliptic shape.

p-0324[Modification 18]

p-0325Modification 18 is an example suitable to appropriately control the gain of a received output signal (such gain is hereinafter referred to as “reception gain”) based on the level or output value of the entire output signals received from the sensor section in the first embodiment.

p-0326In the first embodiment, a signal of a particular frequency component is detected from within an output signal by the synchronous detection circuit <b>37</b> shown in <figref idrefs="DRAWINGS">FIG. 10</figref> of the signal detection circuit <b>34</b>, and the level of the detected signal of the particular frequency component (such signal is hereinafter referred to as “detection signal”) is used (referenced) by an automatic gain control circuit (not shown) or the control circuit <b>40</b> to determine a reception gain. Then, the reception gain is set in the amplification circuit <b>32</b>. However, where a signal other than the particular frequency component, that is, noise, is input to the synchronous detection circuit <b>37</b>, or where a plurality of signals having different frequencies are received, the intensity of a combined signal cannot be obtained readily and the reception gain of the amplification circuit <b>32</b> cannot be set appropriately. As a result, there is the possibility that the output signal may be saturated in the amplification circuit <b>32</b>.

p-0327Therefore, modification 18 provides not only means for detecting a particular frequency component from within output signals of the reception conductors <b>12</b>, but also means for obtaining a signal level of all frequency components of the output signals and, further, means for referring to the signal level of all frequency components to set a reception gain.

p-0328<figref idrefs="DRAWINGS">FIG. 41</figref> shows a block configuration of the reception section of the pointer detection apparatus according to modification 18. <figref idrefs="DRAWINGS">FIG. 42</figref> shows a block configuration of an absolute value detection circuit <b>39</b>A. In the example of <figref idrefs="DRAWINGS">FIG. 41</figref>, an absolute value detection circuit <b>39</b>A for detecting an energy component is given as an example of the means for obtaining the level of all frequency components of the output signals. In the example of <figref idrefs="DRAWINGS">FIG. 42</figref>, an automatic gain control circuit <b>39</b>B for acquiring the level of all frequency components from the absolute value detection circuit is provided as an example of the means for referring to the level of the signal of all frequency components to set a reception gain.

p-0329As seen in <figref idrefs="DRAWINGS">FIGS. 41 and 42</figref>, the absolute value detection circuit <b>39</b>A is provided in the signal detection section <b>34</b><i>a </i>in the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 9</figref>, and the automatic gain control circuit <b>39</b>B is coupled to (or provided in) the absolute value detection circuit <b>39</b>A.

p-0330As seen in <figref idrefs="DRAWINGS">FIG. 42</figref>, the absolute value detection circuit <b>39</b>A includes, as principal components thereof, an input terminal <b>390</b>, a multiplier <b>391</b> for carrying out arithmetic operation of squaring the level of a detection signal or output signal, and an integrator <b>392</b> for integrating the output of the multiplier <b>391</b>. If a detection signal is input from a reception conductor <b>12</b> to an absolute value detection circuit <b>39</b>A through the A/D conversion circuit <b>33</b>, then the detection signal is branched by the input terminal <b>390</b> and supplied to the multiplier <b>391</b>. Both of the two branched detection signals are input to and subjected to squaring operation by the multiplier <b>391</b>. Then, the detection signal squared by the multiplier <b>391</b> is input to and temporarily integrated by the integrator <b>392</b>, and output.

p-0331The absolute value detection may be carried out not by the method of integrating an energy component obtained by squaring an output signal described above, but by another method of integrating the absolute value of the level of the output signal. Any method may be used by which the level of a signal including a signal of all frequency components and noise can be detected. Further, the absolute value detection process may be carried out by any of digital signal processing means and analog circuit means.

p-0332In the present example, the pointer detection apparatus is configured such that the reception gain is set based on the level of a signal obtained by absolute value detection of output signals of the reception conductors <b>12</b>, that is, of a signal of all frequency components. Thus, the level of received signals including a plurality of signals of different frequencies and noise can be detected to set the reception gain appropriately.

p-0333[Modification 19]

p-0334Modification 19 is an example suitable to compensate for a drop of the level or a delay of the phase of a periodic signal due to floating capacitance of the transmission conductors and the reception conductors, which serve as transmission lines, in the first embodiment. Modification 19 is described with reference to <figref idrefs="DRAWINGS">FIGS. 43A</figref>, <b>43</b>B, <b>44</b>A, and <b>44</b>B.

p-0335In the first embodiment, periodic signals are supplied from one side of the transmission conductors <b>14</b>. <figref idrefs="DRAWINGS">FIG. 43A</figref> illustrates a supplying form of periodic signals in a one-side supplying scheme, and <figref idrefs="DRAWINGS">FIG. 43B</figref> shows a graph representing the level of output signals when a periodic signal is applied to a transmission conductor Y_k. In <figref idrefs="DRAWINGS">FIG. 43B</figref>, the axis of abscissa of the graph represents the position of the reception conductors <b>12</b>, and the axis of ordinate represents the level of the output signals.

p-0336As the distance from the supplying side of a periodic signal, in the example of <figref idrefs="DRAWINGS">FIG. 43A</figref>, from the right end of a transmission conductor <b>14</b>, increases, that is, toward the reception conductor X_mremote from the reception conductor X_m+8, which is positioned near to the supplying side of a periodic signal, the level of the output signal drops. Similarly, the phase delay increases from the reception conductor X_m+8side toward the remote reception conductor X_m. A level difference and a phase difference appear between the reception conductor X_m+8near the supplying side of a periodic signal and the reception conductor X_mremote from the supplying side, which causes coordinate displacement upon position calculation. Particularly where the sensor section is formed using ITO, the resistance value of the ITO is high and the sensor section is subjected to a rather substantial influence by the transmission line.

p-0337Therefore, in modification 19, the transmission section including the multi-frequency signal supplying circuit <b>21</b> and the transmission conductor selection circuit <b>22</b> is provided at each of the opposite ends of the transmission conductors <b>14</b> so that periodic signals are supplied at the same time from the left and the right to the transmission conductors <b>14</b>.

p-0338<figref idrefs="DRAWINGS">FIG. 44A</figref> illustrates a supplying form of periodic signals where the transmission sections are provided at the opposite ends of the transmission conductors <b>14</b> in modification 19, and <figref idrefs="DRAWINGS">FIG. 44B</figref> shows a graph representing the level of output signals when a periodic signal is supplied to the transmission conductor Y_kin modification 19. In <figref idrefs="DRAWINGS">FIG. 44B</figref>, the axis of abscissa of the graph represents the position of the reception conductors <b>12</b> and the axis of ordinate represents the level of the output signals.

p-0339As seen in <figref idrefs="DRAWINGS">FIG. 44B</figref>, as the distance from the reception conductors X_mand X_m+8which are positioned near the supplying sections of a periodic signal increases, the level of the output signal drops. Here, since the distance from the reception conductors X_mand X_m+8on the opposite ends of the reception conductors <b>12</b> to the remote reception conductor X_m+4is one half the distance between the reception conductor X_mand the reception conductor X_m+8which are farthest apart in the example of <figref idrefs="DRAWINGS">FIG. 44A</figref>, the level drop of the output signal decreases to one half. Simultaneously, the phase delay decreases to one half.

p-0340In the present example, the periodic signal supplying sections are provided on the opposite sides of the transmission conductors. As an alternative, output signals of the transmission conductor selection circuit <b>22</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref> may be branched so as to be supplied to the opposite ends of the transmission conductors <b>14</b>. As described above, a periodic signal need not be provided to a single transmission conductor <b>14</b> at a time, but may be provided to a plurality of transmission conductors.

p-0341Since a periodic signal is supplied at the same time from the transmission sections provided at the opposite ends of a transmission conductor <b>14</b>, the level drop and the phase delay of the periodic signal can be moderated in comparison with those including a conventional one-side supplying system. Hence, the level difference and the phase difference among the reception conductors <b>12</b> decrease considerably, thereby suppressing the drop in detection sensitivity.

p-0342[Modification 20]

p-0343Modification 20 is suitable to detect a pressure when a pointer touches the detection surface of the sensor section in the first embodiment. A pressure exerted by a pointer is hereinafter referred to as finger pressure (though, of course, a pointer is not limited to a human finger in accordance with the present invention).

p-0344Heretofore, the finger pressure was calculated based on the assumption that it has a proportional relationship to the area on the detection surface of the sensor section that is touched by the finger (hereinafter “touched area”). Therefore, if a person having a small finger and another person having a large finger depress the detection surface with equal force, then the touched area of the person having a small finger is smaller than that of the person having a large finger. In addition, even if the person having a small finger depresses the detection surface with large force, the conventional finger pressure system may recognize it as a light touch. Therefore, in modification 20, the pointer detection apparatus is configured such that the finger pressure exerted by a pointer such as a finger touching the detection surface is detected based on a spatial distribution or level curved face of the level of the detected output signals.

p-0345<figref idrefs="DRAWINGS">FIG. 45A</figref> illustrates an example of a spatial distribution or level curved face of the level of detected output signals when a pointer touches the detection surface of the sensor section.

p-0346The level curved face <b>110</b> of the output signals is determined from the variation of current at cross points of the sensor section. The level curved face <b>110</b> is calculated, for example, by the position calculation circuit <b>35</b> shown in <figref idrefs="DRAWINGS">FIG. 1</figref> which analyzes the output of the signal detection circuit <b>34</b>. Here, the coordinate of a transmission conductor <b>14</b> which is positioned substantially at the center of the touched area at which a high level value is obtained is represented by “0,” and the coordinates of the transmission conductors <b>14</b> disposed from the left to right sides of the centrally positioned transmission conductor <b>14</b> (“0”) are represented by “ . . . , −3, −2, −1, 1, 2, 3, . . . . ” The reception conductors <b>12</b> are similarly arranged. The level values of the level curved face <b>110</b> are in a normalized form. As seen in <figref idrefs="DRAWINGS">FIG. 45A</figref>, the level curved face <b>110</b> exhibits a mountain-like shape having an apex or summit substantially at the center of the touched area, and a finger pressure is estimated using the volume of a portion of (or under) the level curved face <b>110</b> cut across (horizontally in <figref idrefs="DRAWINGS">FIG. 45A</figref>) at a predetermined level value.

p-0347<figref idrefs="DRAWINGS">FIG. 45B</figref> shows one simple method of determining the volume of an upper space when the level curved face <b>110</b> is cut across at a predetermined level, which entails dividing the level curved face <b>110</b> into a plurality of (vertical) planes and determining the volume by summing the area values of the planes, that is, two-dimensional level values of the planes.

p-0348Referring to <figref idrefs="DRAWINGS">FIG. 45B</figref>, an example of division of the level curved face <b>110</b> into a plurality of planes is shown. In the example of <figref idrefs="DRAWINGS">FIG. 45B</figref>, the level curved face <b>110</b> is divided into a plurality of planes <b>111</b> to <b>115</b> along those transmission conductors whose coordinates range from “−2” to “2,” respectively. First, the area of each of the planes <b>111</b> to <b>115</b> is determined, and the areas of the planes <b>111</b> to <b>115</b> are summed to obtain a volume of the level curve <b>101</b>. At this time, the area is determined preferably with regard to those of the planes <b>111</b> to <b>115</b> whose apex levels are higher than the predetermined level value.

p-0349While, in the example described above, the sum of the areas of the planes into which the level curved face is divided is used as the volume of the level curved face, alternatively the level values may be weight-added in a numerical analysis. Further, the calculation method of the volume is not limited to summing up the values associated with divisional planes. The volume may be calculated, for example, by applying multi-dimensional curved face approximation, such as trapezoidal shape approximation and square approximation.

p-0350One method of determining the volume of an upper space of the level curved face <b>110</b> when it is cut out at a predetermined level value is described with reference to <figref idrefs="DRAWINGS">FIG. 46</figref>. <figref idrefs="DRAWINGS">FIG. 46</figref> illustrates a relationship between the position of transmission conductors and the area of divisional planes (as shown in <figref idrefs="DRAWINGS">FIG. 45B</figref>). The axis of abscissa indicates the position of transmission conductors, and the axis of ordinate indicates the area of planes.

p-0351Referring to <figref idrefs="DRAWINGS">FIG. 46</figref>, data points S₁to S₅on a curve <b>120</b> represent the values of areas determined with regard to the planes <b>111</b> to <b>115</b> of <figref idrefs="DRAWINGS">FIG. 45B</figref>, respectively. Further, in <figref idrefs="DRAWINGS">FIG. 46</figref>, the coordinates “−2” to “2” of the transmission conductors and respectively connected by line segments with the corresponding data points S₁to S₅on the curve <b>120</b>. Further, each adjacent ones of the data points S₁to S₅are interconnected by a line segment. Consequently, four trapezoids are formed between the positions “−2” to “2” of the transmission conductors.

p-0352The volume of the level curved face <b>110</b> to be determined corresponds to the area of a portion surrounded by the axis of abscissa of <figref idrefs="DRAWINGS">FIG. 46</figref>, that is, the straight line between the positions “−2” and the “2” of the transmission conductors, and the curve <b>120</b>. To calculate this area, however, the method described above (the level curved face is divided into a plurality of planes and the volume is determined from the sum value of the areas of the planes, that is, the two-dimensional level values of the planes) may be less than satisfactory and contain a rather substantial error because the volume is determined simply by adding the discrete values of the data points S₁to S₅.

p-0353Therefore, in the example of <figref idrefs="DRAWINGS">FIG. 46</figref>, trapezoid approximation is used to determine the sum value of the areas of the four trapezoids, that is, the area of a portion indicated by slanting lines in <figref idrefs="DRAWINGS">FIG. 46</figref>, to approximate the volume of the level curved face <b>110</b>.

p-0354First, a weight value is applied to each data point in accordance with trapezoid approximation. For example, weight <b>1</b> is applies to the data point S₁, <b>2</b> to the data point S₂, <b>2</b> to the data point S₃, <b>2</b> to the data point S₄and <b>1</b> to the data point S₅. The volume V₁is determined by dividing the “sum value of the weighted areas at the transmission conductors, that is, at the data points” by an “average value of the weight values included in the trapezoids.” In particular, the volume V₁is given by: <br />Volume <i>V</i>₁=(1<i>*S+</i>2<i>*S</i>₂+2<i>*S</i>₃+2<i>*S</i>₄+1<i>*S</i>₅)/2

p-0355Here, the average value of the weight values is determined by dividing the “sum total of the weight values at the data points” by the “number of the trapezoids.” In the example above, (1+2+2+2+1)/4=2.

p-0356It is also possible to use square approximation for the calculation. In this instance, weight values applied to the data points are squared to calculate the volume V₂similarly as described above. In particular, the volume V₂is given by: <br />Volume <i>V</i>₂=(1<i>*S</i>₁+4<i>*S</i>₂4<i>*S</i>₃4<i>*S</i>₄1<i>*S</i>₅)/3.5

p-0357Here, the average value of the weight values is obtained by dividing the “sum of square values of the weight values at the data points” by the “number of trapezoids.” In the present example, (1+4+4+4+1)/4=3.5

p-0358Since the error (discrepancy) between the hypotenuses of the four trapezoids and the curve <b>120</b> is small as seen in <figref idrefs="DRAWINGS">FIG. 46</figref>, the error between a calculation result obtained using the trapezoid approximation, that is, the area of the portion indicated by slanting lines, and the actual volume of the level curved face <b>110</b>, becomes small. As a result, the calculation result obtained using the trapezoid approximation indicates an accurate volume in comparison with a calculation result obtained by summing the divisional areas of the planes into which the level curved face is divided. Further, where the approximation calculation is used to determine the volume, the calculation is simpler than that obtained by summing the areas of the divisional planes of the level curved face. Therefore, the load applied to the position calculation circuit <b>35</b> can be reduced.

p-0359The pressure per unit area may be calculated by dividing the volume of the level curved face by the touched area. In this instance, the volume determined as described above can be divided by a touch area <b>110</b>A illustrated in <figref idrefs="DRAWINGS">FIG. 45</figref> to determine the pressure per unit area.

p-0360In the present example, the finger pressure when a pointer (e.g., a finger) touches the detection surface of the sensor section is detected based on the volume determined using the areas of a plurality of planes into which the level curved face is divided, that is, using two-dimensional level values. Use of the determined volume value as the finger pressure allows for accurate finger pressure detection, which is reflective of an actual touching force exerted by a user.

p-0361Various modifications to the first embodiment described heretoabove can be applied also to the second to fourth embodiments to be described below unless a specific restriction is involved.

2. Second Embodiment

Configuration of the Pointer Detection Apparatus

p-0362As described hereinabove in connection with the first embodiment and modifications <b>6</b> to <b>12</b> and <b>15</b> to <b>17</b> to the first embodiment, in the pointer detection apparatus of the present invention, periodic signals of different frequencies from each other can be supplied to a plurality of transmission conductors <b>14</b>, and output signals from a plurality of reception conductors <b>12</b> can be input collectively to one amplifier. Further, a single pointer detection apparatus may selectively incorporate and switch between one or more configurations described above in connection with modifications <b>6</b> to <b>12</b> and <b>15</b> to <b>17</b>, depending on each application, a required sensitivity, or the like. In particular, a single pointer detection apparatus may be configured to selectively vary the supplying form of periodic signals to the transmission conductor group <b>13</b> and the detection form of output signals from the reception conductor group <b>11</b> depending on each application, a required sensitivity, or the like. <figref idrefs="DRAWINGS">FIG. 47</figref> shows an example of such a pointer detection apparatus. In <figref idrefs="DRAWINGS">FIG. 47</figref>, elements like those in the first embodiment described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref> are denoted by like reference characters and overlapping description of them is omitted herein to avoid redundancy.

p-0363Referring to <figref idrefs="DRAWINGS">FIG. 47</figref>, the pointer detection apparatus <b>150</b> of the second embodiment includes a sensor section <b>10</b>, a transmission section <b>151</b>, a reception section <b>153</b>, and a control circuit <b>40</b> for controlling operation of the transmission section <b>151</b> and the reception section <b>153</b>. The sensor section <b>10</b> and the control circuit <b>40</b> respectively have a similar configuration to that in the first embodiment.

p-0364The transmission section <b>151</b> includes a multi-frequency signal supplying circuit <b>21</b>, a transmission conductor connection pattern changeover circuit <b>152</b>, a transmission conductor selection circuit <b>22</b> and a clock generation circuit <b>23</b>. The multi-frequency signal supplying circuit <b>21</b>, transmission conductor selection circuit <b>22</b> and clock generation circuit <b>23</b> respectively have a configuration similar to that in the first embodiment.

p-0365The transmission conductor connection pattern changeover circuit <b>152</b> is a circuit which, for example, selectively changes over (or switches) a supplying form of periodic signals to be supplied to the transmission conductors <b>14</b>. In particular, the transmission conductor connection pattern changeover circuit <b>152</b> suitably selects the number and the position of transmission conductors <b>14</b> to which periodic signals are to be supplied, the frequencies of periodic signals to be supplied, and so forth, in accordance with each application or the like. For example, the transmission conductor connection pattern changeover circuit <b>152</b> selects one of the supplying forms of periodic signals and so forth described above in connection with modifications <b>6</b> to <b>12</b> and <b>15</b> to <b>17</b>. The selection and changeover operation of a supplying form by the transmission conductor connection pattern changeover circuit <b>152</b> is controlled by the control circuit <b>40</b>. A configuration of the transmission conductor connection pattern changeover circuit <b>152</b> is hereinafter described.

p-0366The transmission conductor selection circuit <b>22</b> includes a plurality of switches. The transmission conductor selection circuit <b>22</b> selects an output terminal of the transmission conductor connection pattern changeover circuit <b>152</b> and a corresponding one of the transmission conductors <b>14</b> in response to the supplying form of periodic signals selected by the transmission conductor connection pattern changeover circuit <b>152</b>. The transmission conductor selection circuit <b>22</b> connects the selected output terminal of the transmission conductor connection pattern changeover circuit <b>152</b> and the selected transmission conductor <b>14</b> to each other. The selection and changeover operation of the transmission conductors <b>14</b> by the transmission conductor selection circuit <b>22</b> is controlled by the control circuit <b>40</b>.

p-0367Referring to <figref idrefs="DRAWINGS">FIG. 47</figref>, the reception section <b>153</b> includes a reception conductor selection circuit <b>31</b>, a reception conductor connection pattern changeover circuit <b>154</b>, an amplification circuit <b>32</b>, an A/D conversion circuit <b>33</b>, a signal detection circuit <b>34</b> and a position calculation circuit <b>35</b>. The reception conductor selection circuit <b>31</b>, amplification circuit <b>32</b>, A/D conversion circuit <b>33</b>, signal detection circuit <b>34</b> and position calculation circuit <b>35</b> respectively have a configuration similar to that in the first embodiment.

p-0368The reception conductor connection pattern changeover circuit <b>154</b> is a circuit which, for example, selectively changes over (or switches) a detection form of output signals from the reception conductor group <b>11</b> in response to a supplying form of periodic signals to the transmission conductors <b>14</b>. In particular, the reception conductor connection pattern changeover circuit <b>154</b> suitably selects the number and the positional relationship of reception conductors <b>12</b> to be connected to one amplifier, a process such as addition or subtraction to be carried out by the amplifier, and so forth, in response to the supplying form of periodic signals, each application, and so forth. For example, the reception conductor connection pattern changeover circuit <b>154</b> selects one of the detection forms of an output signal described above in connection with modifications <b>6</b> to <b>12</b> and <b>15</b> to <b>17</b>. The selection and changeover operation of a supplying form by the reception conductor connection pattern changeover circuit <b>154</b> is controlled by the control circuit <b>40</b>.

p-0369The reception conductor selection circuit <b>31</b> is a circuit section that includes a plurality of switches and selectively connects input terminals of the reception conductor connection pattern changeover circuit <b>154</b> to corresponding ones of the reception conductors <b>12</b>, in response to the detection form of output signals selected by the reception conductor connection pattern changeover circuit <b>154</b>. The selection and changeover operation of the reception conductors <b>12</b> by the reception conductor selection circuit <b>31</b> is controlled by the control circuit <b>40</b>.

p-0370[Changeover (Switching) of the Transmission Conductors]

p-0371Where a configuration described above is adopted, one pointer detection apparatus can suitably set a supplying form of periodic signals to the transmission conductor group <b>13</b> and a detection form of output signals from the reception conductor group <b>11</b> depending on each application, a required sensitivity, and so forth.

p-0372While in the first embodiment described above, one transmission conductor <b>14</b> is selected for every predetermined period of time from within each transmission block <b>25</b> (refer to <figref idrefs="DRAWINGS">FIGS. 1 and 5</figref>) of the transmission conductor group <b>13</b>, in the present second embodiment, periodic signals of different frequencies are supplied at the same time to all transmission conductors <b>14</b> which form a transmission block, to carry out position detection. Then, after every predetermined period of time, a new transmission block is selected, to which periodic signals having different frequencies are supplied at the same time to carry out position detection.

p-0373In the following, an example of switching of transmission conductors by the present embodiment is described with reference to <figref idrefs="DRAWINGS">FIGS. 48</figref>, <b>49</b>A and <b>49</b>B. In the present example, one transmission block <b>161</b> includes 16 transmission conductors <b>14</b> positioned adjacent to each other. Since one transmission block <b>161</b> includes 16 adjacent transmission conductors <b>14</b>, the number of frequencies f_kof periodic signals to be supplied to each of the transmission blocks <b>161</b> is “16.” Accordingly, the number of periodic signal production sections in the multi-frequency signal supplying circuit <b>21</b> (refer to <figref idrefs="DRAWINGS">FIG. 47</figref>) which supply the periodic signals is 16. Since the switching operation illustrated in <figref idrefs="DRAWINGS">FIG. 49B</figref> is different from that illustrated in <figref idrefs="DRAWINGS">FIG. 49A</figref> only in that the direction of rotation of the switching operation of the transmission blocks <b>161</b> is reversed, description is given only of the example of <figref idrefs="DRAWINGS">FIG. 49A</figref>.

p-0374As seen in <figref idrefs="DRAWINGS">FIG. 48</figref>, the transmission conductor connection pattern changeover circuit <b>152</b> includes 16 switches <b>152</b><i>a</i>. The transmission conductor connection pattern changeover circuit <b>152</b> is provided between the multi-frequency signal supplying circuit <b>21</b> and the transmission conductor selection circuit <b>22</b> and receives periodic signals supplied thereto from the multi-frequency signal supplying circuit <b>21</b>.

p-0375The switches <b>152</b><i>a </i>are provided in order to supply periodic signals received from the multi-frequency signal supplying circuit <b>21</b> to the transmission conductors <b>14</b>, which form a transmission block <b>161</b>. The switches <b>152</b><i>a </i>are individually connected to frequency production sections <b>24</b> of the multi-frequency signal supplying circuit <b>21</b> (refer to <figref idrefs="DRAWINGS">FIG. 47</figref>). The transmission conductor connection pattern changeover circuit <b>152</b> carries out switching operation under the control of the control circuit <b>40</b>.

p-0376<figref idrefs="DRAWINGS">FIGS. 49A and 49B</figref> illustrate an example of switching operation of the transmission conductors.

p-0377First, a state where periodic signals of frequencies f₀to f₁₅are supplied at the same time to transmission conductors Y₀to Y₁₅of the transmission block (Y₀to Y₁₅) is described in reference to <figref idrefs="DRAWINGS">FIG. 49A</figref>.

p-0378The periodic signals of the frequencies f₀to f₁₅, output from the frequency production sections <b>24</b> (refer to <figref idrefs="DRAWINGS">FIGS. 3 and 47</figref>) of the multi-frequency signal supplying circuit <b>21</b>, are supplied to the transmission conductors Y₀to Y₁₅of the transmission block {Y₀to Y₁₅} through the switches <b>152</b><i>a</i>, which form the transmission conductor connection pattern changeover circuit <b>152</b>. While the periodic signals of the frequencies f₀to f₁₅are supplied to the reception section <b>153</b>, the reception section <b>153</b> carries out position detection. After the position detection is carried out by the reception section <b>153</b>, the transmission conductor connection pattern changeover circuit <b>152</b> switches to the next transmission block, {Y₁₆to Y₃₁} for example, to which the periodic signals are to be supplied, under the control of the control circuit <b>40</b>. Thus, the periodic signals of the frequencies f₀to f₁₅are supplied to the transmission conductors Y₁₆to Y₃₁, respectively, at the same time. Then, after every predetermined interval of time, the transmission conductor connection pattern changeover circuit <b>152</b> switches to the subsequent transmission block <b>161</b>, to which the periodic signals are to be supplied, i.e., to the transmission block {Y₃₂to Y₄₇}, and so forth, and position detection is repeated for each new transmission block. Then, if the supply of the periodic signals to the last transmission block {Y₄₈to Y₆₃} and the position detection therewith are completed, the transmission conductor connection pattern changeover circuit <b>152</b> switches to the first transmission block, {Y₀to Y₁₅}, to which the periodic signals are to be again supplied, under the control of the control circuit <b>40</b>, and the switching operation described above is repeated. In the present example, the transmission block, to which the periodic signals are to be supplied, returns to the original (first) transmission block in the fourth switching operation.

p-0379Where the switching operation of the transmission conductors <b>14</b>, the transmission conductor selection circuit <b>22</b>, and the transmission conductor connection pattern changeover circuit <b>152</b> are configured as described above, the following effect can be achieved. For example, if one transmission conductor <b>14</b> is selected after a predetermined time interval ΔT from each transmission block of the transmission conductor group <b>13</b> as in the first embodiment, the difference in detection time between those transmission conductors <b>14</b> which are positioned on each boundary between the transmission blocks <b>161</b> becomes great (e.g., the detection time differs greatly between Y₁₅and Y₁₆). This will be described with a specific example below.

p-0380In this example, it is assumed that a pointer is positioned between the transmission conductors Y₁₅and Y₁₆in the first embodiment, and that the periodic signals supplied from the multi-frequency signal supplying circuit <b>21</b> are supplied to the transmission conductors Y₀through Y₆₃in their corresponding transmission blocks {Y₀to Y₁₅}, {Y₁₆to Y₃₁}, {Y₃₂to Y₄₇}, {Y₄₈to Y₆₃}, respectively (refer to <figref idrefs="DRAWINGS">FIG. 48</figref>). The pointer is detected by the reception section <b>30</b>, and the transmission conductor selection circuit <b>22</b> switches to the transmission conductors <b>14</b> successively in a direction in which the index increases after every predetermined time interval ΔT under the control of the control circuit <b>40</b> to detect the position of the pointer. In this instance, the time difference after the periodic signals supplied from the multi-frequency signal supplying circuit <b>21</b> are supplied to the transmission conductors Y₁₅and Y₁₆until the periodic signals are supplied to the transmission conductors Y₁₅and Y₁₆subsequently, is 16ΔT. In this instance, if the pointer is moving in proximity to the boundary between transmission blocks <b>161</b> (e.g., between the transmission conductors Y₁₅and Y₁₆), the detection accuracy of the pointer is decreased.

p-0381In contrast, in the present second embodiment, since the transmission conductors <b>14</b> are switched per a unit of transmission block <b>161</b>, the difference in detection time between the transmission conductors <b>14</b> positioned on the boundary between transmission blocks <b>161</b> is short (ΔT). As a result, even if the pointer is moving in proximity to the boundary between transmission blocks <b>161</b>, the pointer can be detected with a higher degree of accuracy.

p-0382[Changeover (Switching) of the Reception Conductors]

p-0383In the first embodiment described above, one reception conductor <b>12</b> is selected from within each of the detection blocks <b>36</b> of the reception conductor group <b>11</b> after every predetermined period of time. In the present second embodiment, position detection is carried out at the same time for each detection block, and after a predetermined interval of time, position detection is carried out with regard to another detection block.

p-0384An example of the switching of reception conductors in the second embodiment is described with reference to <figref idrefs="DRAWINGS">FIGS. 50 and 51</figref>. It is assumed that one detection block <b>163</b> is formed from 16 reception conductors <b>12</b> that are positioned adjacent to each other. Since one detection block <b>163</b> is formed from 16 reception conductors <b>12</b> positioned adjacent to each other, the number of IN conversion circuits <b>32</b><i>a </i>(i.e., amplifiers) in the amplification circuit <b>32</b> is equal to the number of the reception conductors <b>12</b> which form the detection block <b>163</b>. In other words, the number of the IN conversion circuits <b>32</b><i>a </i>in the amplification circuit <b>32</b> is 16.

p-0385<figref idrefs="DRAWINGS">FIG. 50</figref> shows an example of a configuration of a reception conductor connection pattern changeover circuit <b>154</b> which carries out the switching operation in the present example. The reception conductor connection pattern changeover circuit <b>154</b> includes 16 switches <b>154</b><i>a</i>. The reception conductor connection pattern changeover circuit <b>154</b> is provided between the reception conductor selection circuit <b>31</b> and the amplification circuit <b>32</b>, and receives reception signals supplied thereto from the reception conductor selection circuit <b>31</b>.

p-0386The switches <b>154</b><i>a </i>supply reception signals supplied thereto from the reception conductor selection circuit <b>31</b> at the same time to the IN conversion circuits <b>32</b><i>a</i>, which form the amplification circuit <b>32</b>. The switches <b>154</b><i>a </i>are respectively connected to the I/V conversion circuits <b>32</b><i>a </i>of the amplification circuit <b>32</b>. The reception conductor connection pattern changeover circuit <b>154</b> carries out the switching operation under the control of the control circuit <b>40</b> shown in <figref idrefs="DRAWINGS">FIG. 47</figref>.

p-0387An example of the switching operation of the reception conductors is illustrated in <figref idrefs="DRAWINGS">FIG. 51</figref>. Referring to <figref idrefs="DRAWINGS">FIG. 51</figref>, the reception conductor connection pattern changeover circuit <b>154</b> switches (i.e., changes over) the switches <b>154</b><i>a </i>under the control of the control circuit <b>40</b> to connect all reception conductors <b>12</b> in the detection block {X₀to X₁₅} to the I/V conversion circuits <b>32</b><i>a </i>forming the amplification circuit <b>32</b>, as shown in <figref idrefs="DRAWINGS">FIG. 9</figref>. Then, the reception section <b>153</b> carries out position detection of a pointer at the same time with regard to all of the connected reception conductors <b>12</b> within the detection block.

p-0388After the reception section <b>153</b> completes the position detection, the reception conductor connection pattern changeover circuit <b>154</b> switches the switches <b>154</b><i>a </i>to be connected from the previous detection block {X₀to X₁₅} to the next detection block {X₁₆to X₃₁}, to thereby connect all of the reception conductors <b>12</b> in the next detection block <b>163</b> to the I/V conversion circuits <b>32</b><i>a </i>under the control of the control circuit <b>40</b>. Then, the reception section <b>153</b> carries out position detection of a pointer at the same time with regard to all of the connected reception conductors <b>12</b> within the next detection block. Thereafter, the switching operation described is carried out repetitively. When the position detection with regard to the last detection block {X₁₁₂to X₁₂₇} ends, the reception conductor connection pattern changeover circuit <b>154</b> switches the switches <b>154</b><i>a</i>, under the control of the control circuit <b>40</b>, to again connect the first detection block {X₀to X₁₅} to the IN conversion circuits <b>32</b><i>a</i>, and repeats the switching operation described above. In this example, the reception conductor connection pattern changeover circuit <b>154</b> returns to the same (e.g., the first) detection block in the eighth switching operation.

p-0389Where the switching operation of the reception conductors <b>12</b>, the reception conductor selection circuit <b>31</b>, and the reception conductor connection pattern changeover circuit <b>154</b> are configured as described above, the following effect can be achieved. In particular, if one reception conductor <b>12</b> is selected after every predetermined time interval Δt from within each detection block of the reception conductor group <b>11</b> as in the first embodiment, the difference in detection time between those reception conductors <b>12</b>, which are positioned on each boundary between the detection blocks, becomes great (e.g., the detection time differs greatly between X₁₅and X₁₆). More particularly, if the reception conductors X₀, X₁₆, . . . , X₁₁₂are detected in the detection blocks {X₀to X₁₅}, {X₁₆to X₃₁}, . . . , {X₁₁₂to X₁₂₇}, respectively, and the reception conductors <b>12</b> are switched successively in the direction in which the index increases after every predetermined time interval Δt, the detection time difference between the reception conductors X₁₅(the 16^thin the first detection block) and X₁₆(the 1^stin the second detection block) is as great as 15 Δt. In this instance, if a pointer is moving in proximity to the boundary between detection blocks such as between the reception conductors X₁₅and X₁₆, the detection accuracy of the pointer is decreased due to the large detection time difference between the two reception conductors.

p-0390In contrast, in the present embodiment, since the reception conductors <b>12</b> are switched per a unit of detection block <b>163</b>, the difference in detection time between reception conductors <b>12</b>, which are positioned on the boundary between the detection blocks <b>163</b>, becomes as short as Δt. As a result, even if a pointer is moving in proximity to the boundary between detection blocks, the pointer can be detected with a high degree of accuracy.

p-0391[Modification 1]

p-0392In modification 1 of the second embodiment, another example of rotation of the switching operation of the transmission conductors <b>14</b> is applied. The pointer detection apparatus in modification 1 has the same configuration as that of the second embodiment, and therefore, the description of the same is omitted herein to avoid redundancy.

p-0393Modification 1 is different from the second embodiment in that, while in the rotation in the second embodiment, the changeover (switching) of the 16 switches <b>152</b><i>a </i>which form the transmission conductor connection pattern changeover circuit <b>152</b> is carried out per a unit of transmission block <b>161</b>, in the rotation in modification 1, the switching is carried out by successively shifting the 16 switches <b>152</b><i>a </i>one by one in a direction in which the index of the transmission conductor <b>14</b> decreases (or increases). Examples of the rotation of the switching operation of the transmission conductors in modification 1 are illustrated in <figref idrefs="DRAWINGS">FIGS. 53A and 53B</figref>. The switching operation in <figref idrefs="DRAWINGS">FIG. 53B</figref> is different from that in <figref idrefs="DRAWINGS">FIG. 53A</figref> only in that the direction of rotation of the switching operation is reverse to that in the example of <figref idrefs="DRAWINGS">FIG. 53A</figref>. Therefore, description is given only of the example of <figref idrefs="DRAWINGS">FIG. 53A</figref>.

p-0394First, the periodic signals of the frequencies f₀to f₁₅supplied from the multi-frequency signal supplying circuit <b>21</b> are supplied at the same time to the and Y₆₃which are positioned adjacent to each other, that is, which have consecutive indexes n. While the periodic signals of the frequencies f₀to f₁₅remain supplied, the reception section <b>30</b> carries out position detection.

p-0395After a predetermined interval of time, the control circuit <b>40</b> controls the transmission conductor connection pattern changeover circuit <b>152</b> to switch the transmission conductors, to which the frequencies f₀to f₁₅are to be supplied via the switches <b>152</b><i>a</i>, by one transmission conductor in a direction in which the index n decreases. (Switches <b>152</b><i>a </i>form the transmission conductor connection pattern changeover circuit <b>152</b>.) In particular, the periodic signals of the frequencies f₀to f₁₅are now supplied at the same time to the transmission conductors Y₄₇to Y₆₂, respectively. While the periodic signals of the frequencies f₀to f₁₅remain supplied, the reception section <b>153</b> carries out position detection. Such switching operation is repeated until the periodic signals of the frequencies f₀to f₁₅are supplied to the transmission conductors Y₀to Y₁₅, respectively, and the reception section <b>153</b> carries out position detection. Thereafter, the control circuit <b>40</b> controls the transmission conductor connection pattern changeover circuit <b>152</b> to switch the transmission conductors connected to the switches <b>152</b><i>a</i>, from the transmission conductors Y₀and Y₁to Y₁₅to the transmission conductors Y₆₃and Y₀to Y₁₄, respectively. Then, the reception section <b>153</b> carries out position detection operation similar to that described above.

p-0396With such rotation of the switching operation of the transmission conductors <b>14</b> as in the present example, the following effect can be achieved. In particular, periodic signals are supplied to 16 transmission conductors positioned adjacent to each other, and a group formed of 16 transmission conductors positioned adjacent to each other is shifted by one transmission conductor such that position detection is carried out in a concentrated manner at a particular portion. Therefore, the detection accuracy can be improved.

3. Third Embodiment

p-0397In a third embodiment, another example of rotation of switching operation of transmission conductors <b>14</b> is used. The pointer detection apparatus of the third embodiment has the same configuration as that of the first embodiment, and therefore, overlapping description of the configuration is omitted herein to avoid redundancy.

p-0398The third embodiment is different from the first embodiment in that, while the rotation in the first embodiment is carried out such that each of the frequencies f₀to f₁₅supplied from the multi-frequency signal supplying circuit <b>21</b> is supplied to a fixed one of the transmission blocks <b>25</b>, as seen in <figref idrefs="DRAWINGS">FIG. 5</figref>, the rotation in the third embodiment is carried out such that periodic signals to be supplied to transmission blocks may vary (i.e., each of the frequencies may be supplied to different transmission blocks). <figref idrefs="DRAWINGS">FIGS. 52A and 52B</figref> illustrate examples of the rotation of the switching operation of transmission conductors according to the third embodiment. The switching operation in <figref idrefs="DRAWINGS">FIG. 52B</figref> is different from that in <figref idrefs="DRAWINGS">FIG. 52A</figref> only in that the direction of rotation of the switching operation is reverse to that in the example of <figref idrefs="DRAWINGS">FIG. 52A</figref>. Therefore, description is given only of the example of <figref idrefs="DRAWINGS">FIG. 52A</figref>.

p-0399First, periodic signals of the frequencies f₀to f₁₅, supplied from the multi-frequency signal supplying circuit <b>21</b>, are supplied at the same time to those transmission conductors <b>14</b> which respectively have the highest index within their corresponding transmission blocks <b>25</b> (each including four transmission conductors <b>14</b>), that is, to the transmission conductors Y₃, Y₂, . . . , Y₅₉, Y₆₃, respectively. Then, while the periodic signals of the frequencies f₀to f₁₅are supplied, the reception section <b>30</b> carries out position detection.

p-0400After a predetermined interval of time, the transmission conductors to which the frequencies f₀to f₁₅are to be supplied are switched (or shifted) by one transmission conductor in a direction in which the index n decreases. In particular, the transmission conductors to which the frequencies f₀to f₁₅are to be supplied are switched from the transmission conductors Y₃, Y₇, . . . , Y₅₅, Y₅₉and Y₆₃selected in the preceding cycle to the transmission conductors Y₂, Y₆, . . . , Y₅₄, Y₅₈and Y₆₂. Then, the periodic signals of the frequencies f₀to f₁₅are supplied at the same time to the transmission conductors Y₂, Y₆, . . . , Y₅₄, Y₅₈and Y₆₂. While the periodic signals of the frequencies f₀to f₁₅are supplied, the reception section <b>30</b> carries out position detection. Such switching operation is repeated until the periodic signals of the frequencies f₀to f₁₅are supplied to the transmission conductors Y₀, Y₄, . . . , Y₅₄, Y₅₈and Y₆₀and the reception section <b>30</b> carries out position detection. Thereafter, the control circuit <b>40</b> controls the multi-frequency signal supplying circuit <b>21</b> to change the frequencies of the periodic signals to be supplied from the frequency production sections <b>24</b> of the multi-frequency signal supplying circuit <b>21</b> to the transmission blocks <b>25</b>. In particular, the periodic signals of the frequencies f₀, f₁, . . . , f₁₃, f₁₄and f₁₅supplied from the transmission blocks <b>25</b> are next supplied to the transmission conductors Y₆₃, Y₃, . . . , Y₅₁, Y₅₅and Y₅₉, respectively. Then, position detection operation is carried out similarly as described above. Switching of the transmission conductors is carried out in this manner in the third embodiment.

p-0401With rotation of the switching operation of the transmission conductors <b>14</b> as in the present example, the following effect is achieved. In particular, in the examples illustrated in <figref idrefs="DRAWINGS">FIGS. 48</figref>, <b>49</b>A and <b>49</b>B in the second embodiment, since periodic signals of sixteen different frequencies are respectively supplied at the same time to 16 transmission conductors positioned adjacent to each other, position detection is carried out in a concentrated manner for a particular portion of the sensor section <b>10</b> at a certain point of time. However, for any portion other than the particular portion, position detection cannot be carried out. In contrast, in the third embodiment, periodic signals having different frequencies are respectively supplied to those transmission conductors, which are spaced apart from each other by a predetermined number of transmission conductors (in the present example, by three transmission conductors), across the entire set of transmission conductors (in the present example, 64 transmission conductors) (as in the first embodiment). Further, the transmission conductors to which the periodic signals having different frequencies are to be supplied are successively shifted or displaced with respect to the entire set of transmission conductors (i.e., each frequency signal is successively supplied to each of the entire set of transmission conductors). As a result, since the periodic signals of the different frequencies are supplied to every third transmission conductor, the position of a pointer can be detected in a well-balanced manner over the entire sensor section <b>10</b>.

p-0402A rotation of the switching operation similar to that described above with respect to the transmission conductors <b>14</b> may be applied with respect to the reception conductors <b>12</b>. Specifically, in the reception section, outputs from those of the reception conductors, which are spaced apart by a predetermined number of reception conductors (such as seven reception conductors) among the complete set of reception conductors (such as 128 reception conductors) may be detected. Then, these reception conductors for output detection are successively shifted or displaced among the complete set of transmission conductors similarly as in the rotation of the switching operation of the transmission conductors <b>14</b>. With this configuration, an effect similar to that of the transmission section, as described above, can be achieved.

p-0403In all of the embodiments described above, including the examples of <figref idrefs="DRAWINGS">FIG. 6</figref> (the first embodiment), <figref idrefs="DRAWINGS">FIGS. 49A</figref>, <b>49</b>B (the second embodiment), <figref idrefs="DRAWINGS">FIGS. 53A</figref>, <b>53</b>B (Modification 1 to the second embodiment), and <figref idrefs="DRAWINGS">FIGS. 52A</figref>, <b>52</b>B (the third embodiment), signals of different frequencies produced by the multi-frequency signal production circuit are supplied to predetermined ones of a plurality of transmission conductors <b>14</b>, between which a predetermined number P (P is an integer which satisfies P≧0) of transmission conductors are interposed, and such predetermined conductors are successively switched.

p-0404Further, predetermined ones of a plurality of reception conductors <b>12</b> between which a predetermined number R (R is an integer which satisfies R≧0) are interposed are selected, and the predetermined conductors are successively switched.

4. Fourth Embodiment

p-0405A fourth embodiment of the present invention is configured to suppress a composite amplitude or beat phenomenon, where a plurality of periodic signals of different frequencies are supplied in a superposed relationship to a signal detection circuit according to the first to third embodiments.

p-0406It is assumed in the first to third embodiments that the initial phases of a plurality of periodic signals of different frequencies to be supplied at the same time to the transmission conductors are adjusted (or set) to 0 degree. Since the reception section <b>30</b> receives a plurality of periodic signals of different frequencies as a composite signal of the periodic signals, significant beats may be produced from the periodic signals. As a result, there is a possibility that the periodic signals may exceed the dynamic range of the reception section <b>30</b>, causing saturation in the reception section <b>30</b>. Further, if the level of the detected output signal is adjusted so as not to cause saturation in the reception section <b>30</b>, there is the possibility that a desired detection sensitivity may not be obtained.

p-0407Therefore, in the fourth embodiment, the pointer detection apparatus includes phase controlling means for controlling the phase of periodic signals to be output from the multi-frequency signal production section, so that transmission starting phases of a plurality of periodic signals are dispersed to thereby suppress beats.

p-0408<figref idrefs="DRAWINGS">FIG. 54</figref> shows a general configuration of the pointer detection apparatus according to the fourth embodiment. Referring to <figref idrefs="DRAWINGS">FIG. 54</figref>, the pointer detection apparatus <b>200</b> includes, as principal components thereof, a sensor section <b>10</b>, a transmission section <b>210</b>, a reception section <b>30</b>, a position calculation circuit <b>35</b>, and a control circuit <b>40</b> for controlling operation of the transmission section <b>210</b> and the reception section <b>30</b>. In <figref idrefs="DRAWINGS">FIG. 54</figref>, elements like those of the pointer detection apparatus <b>100</b> described above with reference to <figref idrefs="DRAWINGS">FIG. 1</figref> are denoted by like reference characters and overlapping description of them is omitted herein to avoid redundancy.

p-0409The transmission section <b>210</b> includes a phase controlling circuit <b>211</b>, a multi-frequency signal supplying circuit <b>21</b>, a transmission conductor selection circuit <b>22</b> and a clock generation circuit <b>23</b>. The multi-frequency signal supplying circuit <b>21</b>, transmission conductor selection circuit <b>22</b> and clock generation circuit <b>23</b> have a configuration similar to that in the first embodiment.

p-0410The phase controlling circuit <b>211</b> changes the phases of periodic signals produced by the multi-frequency signal supplying circuit <b>21</b> and supplies the periodic signals of the changed phases to the transmission conductors <b>14</b>. For example, the phase controlling circuit <b>211</b> can set initial phases used in the periodic signal production sections <b>24</b> in the multi-frequency signal supplying circuit <b>21</b> of <figref idrefs="DRAWINGS">FIG. 4</figref>. In particular, the multi-frequency signal supplying circuit <b>21</b> of the pointer detection apparatus <b>100</b> of <figref idrefs="DRAWINGS">FIG. 1</figref> controls the values of the initial phases to be provided to the periodic signal production sections <b>24</b> to carry out a phase adjustment process The control circuit <b>40</b> controls a degree by which the phase controlling circuit <b>211</b> shifts the phase of any periodic signal.

p-0411In the following, phase control over the transmission starting phases is described in connection with an example which involves two frequencies.

p-0412<figref idrefs="DRAWINGS">FIG. 55</figref> illustrates waveforms of a periodic signal of a frequency f_oand another periodic signal of another frequency f₁where the transmission starting phase of the periodic signal of the frequency f₁is displaced from that of the frequency signal of the frequency f₀so that the transmission starting phases are dispersed. In the present example, adjacent periodic signals have opposite phases. In this manner, multiple periodic signals having different frequencies should be combined such that their transmission starting phases are displaced from each other and, further, adjacent periodic signals have opposite phases. As a result, the periodic signals cancel each other at a rising edge or a falling edge of waveforms upon starting of transmission or upon ending of transmission, to thereby prevent an excessively high output signal (due to beat, for example) from flowing into the reception section <b>30</b>.

p-0413While the present example described involves two frequencies for the convenience of description, the number of frequencies is not limited to two, but may be greater than two. A dispersion of transmission starting phases in the case of a plurality of frequencies is hereinafter described. Where the number of frequencies is an odd number, the transmission starting phase of the frequency, which is left out after the rest of the frequencies are combined into one or more pairs, should be set to 0 degree or 180 degrees.

p-0414The method of the phase control is not limited to the example described above. For example, the phase controlling circuit <b>211</b> may be configured from 16 phase shifters (not shown) in a corresponding relationship to the periodic signal production sections <b>24</b>, respectively, in the multi-frequency signal supplying circuit <b>21</b> of <figref idrefs="DRAWINGS">FIG. 3</figref>. Alternatively, the phase controlling circuit <b>211</b> may include 45-degree phase shifting circuits, signal inversion circuits, or switches (not shown), so as to selectively control the number of phase shifts by the phase shifting circuits or the phase inversion by the signal inversion circuits to thereby carry out a phase control by 45 degrees or by 90 degrees.

p-0415In the following, modes of a plurality of transmission starting phases of different periodic signals are described.

p-0416<figref idrefs="DRAWINGS">FIGS. 56 to 61</figref> illustrate composite waveforms of a plurality of periodic signals after a phase control is carried out where the initial phases of the periodic signals are varied in different patterns. In these examples, 16 periodic signals of different frequencies from 100 kHz to 250 kHz are generated by the multi-frequency signal supplying circuit <b>21</b> in a corresponding relationship to the number of transmission blocks, that is, 16, and the reception period by the reception section <b>30</b> is 200 ns.

p-0417<figref idrefs="DRAWINGS">FIG. 56</figref> illustrates an example of a composite waveform of 16 periodic signals of different frequencies where no phase dispersion is applied (refer to Table 1 below). In other words, <figref idrefs="DRAWINGS">FIG. 56</figref> illustrates the composite waveform where 16 periodic signals of wavelengths from 100 kHz to 250 kHz are supplied without carrying out any phase control.

p-0418<tables id="TABLE-US-00001" num="00001"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 1</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: No</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>0</entry></row><row><entry>3</entry><entry>120</entry><entry>0</entry></row><row><entry>4</entry><entry>130</entry><entry>0</entry></row><row><entry>5</entry><entry>140</entry><entry>0</entry></row><row><entry>6</entry><entry>150</entry><entry>0</entry></row><row><entry>7</entry><entry>160</entry><entry>0</entry></row><row><entry>8</entry><entry>170</entry><entry>0</entry></row><row><entry>9</entry><entry>180</entry><entry>0</entry></row><row><entry>10</entry><entry>190</entry><entry>0</entry></row><row><entry>11</entry><entry>200</entry><entry>0</entry></row><row><entry>12</entry><entry>210</entry><entry>0</entry></row><row><entry>13</entry><entry>220</entry><entry>0</entry></row><row><entry>14</entry><entry>230</entry><entry>0</entry></row><row><entry>15</entry><entry>240</entry><entry>0</entry></row><row><entry>16</entry><entry>250</entry><entry>0</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00001">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0419<figref idrefs="DRAWINGS">FIG. 57</figref> illustrates an example of a composite waveform where phase dispersion is applied for every 90 degrees to 16 periodic signals of different frequencies (pattern 0: refer to Table 2 below). Referring to <figref idrefs="DRAWINGS">FIG. 57</figref>, in the example illustrated, 90-degree phase shifting is applied to achieve phase dispersion.

p-0420<tables id="TABLE-US-00002" num="00002"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 2</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: pattern 0 (for every 90 degrees)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>90</entry></row><row><entry>3</entry><entry>120</entry><entry>180</entry></row><row><entry>4</entry><entry>130</entry><entry>270</entry></row><row><entry>5</entry><entry>140</entry><entry>0</entry></row><row><entry>6</entry><entry>150</entry><entry>90</entry></row><row><entry>7</entry><entry>160</entry><entry>180</entry></row><row><entry>8</entry><entry>170</entry><entry>270</entry></row><row><entry>9</entry><entry>180</entry><entry>0</entry></row><row><entry>10</entry><entry>190</entry><entry>90</entry></row><row><entry>11</entry><entry>200</entry><entry>180</entry></row><row><entry>12</entry><entry>210</entry><entry>270</entry></row><row><entry>13</entry><entry>220</entry><entry>0</entry></row><row><entry>14</entry><entry>230</entry><entry>90</entry></row><row><entry>15</entry><entry>240</entry><entry>180</entry></row><row><entry>16</entry><entry>250</entry><entry>270</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00002">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0421<figref idrefs="DRAWINGS">FIG. 58</figref> illustrates an example of a composite waveform where phase dispersion is applied for every ±90 degrees to 16 periodic signals of different frequencies (pattern 1: refer to Table 3 below). Referring to <figref idrefs="DRAWINGS">FIG. 58</figref>, in the example illustrated, 90-degree phase shifting and phase reversal are selectively applied to achieve phase dispersion.

p-0422<tables id="TABLE-US-00003" num="00003"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 3</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: pattern 1 (for every ±90 degrees)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>180</entry></row><row><entry>3</entry><entry>120</entry><entry>90</entry></row><row><entry>4</entry><entry>130</entry><entry>270</entry></row><row><entry>5</entry><entry>140</entry><entry>0</entry></row><row><entry>6</entry><entry>150</entry><entry>180</entry></row><row><entry>7</entry><entry>160</entry><entry>90</entry></row><row><entry>8</entry><entry>170</entry><entry>270</entry></row><row><entry>9</entry><entry>180</entry><entry>0</entry></row><row><entry>10</entry><entry>190</entry><entry>180</entry></row><row><entry>11</entry><entry>200</entry><entry>90</entry></row><row><entry>12</entry><entry>210</entry><entry>270</entry></row><row><entry>13</entry><entry>220</entry><entry>0</entry></row><row><entry>14</entry><entry>230</entry><entry>180</entry></row><row><entry>15</entry><entry>240</entry><entry>90</entry></row><row><entry>16</entry><entry>250</entry><entry>270</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00003">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0423<figref idrefs="DRAWINGS">FIG. 59</figref> illustrates an example of a composite waveform where phase dispersion is applied for every +45 degrees to 16 periodic signals of different frequencies (pattern 2-1: refer to Table 4 below). Referring to <figref idrefs="DRAWINGS">FIG. 59</figref>, in the example illustrated, 45-degree phase shifting and phase reversal are selectively applied to achieve phase dispersion.

p-0424<tables id="TABLE-US-00004" num="00004"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 4</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: pattern 2-1 (for every ±45 degrees)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>180</entry></row><row><entry>3</entry><entry>120</entry><entry>45</entry></row><row><entry>4</entry><entry>130</entry><entry>315</entry></row><row><entry>5</entry><entry>140</entry><entry>90</entry></row><row><entry>6</entry><entry>150</entry><entry>270</entry></row><row><entry>7</entry><entry>160</entry><entry>135</entry></row><row><entry>8</entry><entry>170</entry><entry>225</entry></row><row><entry>9</entry><entry>180</entry><entry>0</entry></row><row><entry>10</entry><entry>190</entry><entry>180</entry></row><row><entry>11</entry><entry>200</entry><entry>45</entry></row><row><entry>12</entry><entry>210</entry><entry>315</entry></row><row><entry>13</entry><entry>220</entry><entry>90</entry></row><row><entry>14</entry><entry>230</entry><entry>270</entry></row><row><entry>15</entry><entry>240</entry><entry>135</entry></row><row><entry>16</entry><entry>250</entry><entry>225</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00004">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0425<figref idrefs="DRAWINGS">FIG. 60</figref> illustrates an example of a composite waveform where phase dispersion is applied for every ±45 degrees to 16 periodic signals of different frequencies (pattern 2-2: refer to Table 5 below). Referring to <figref idrefs="DRAWINGS">FIG. 60</figref>, in the example illustrated, 45-degree phase shifting and phase reversal are selectively applied to the periodic signals to be supplied to the first (1^st) to eighth (8^th) transmission blocks. Further, 45-degree phase shifting and phase reversal are selectively applied to the periodic signals to be supplied to the ninth (9^th) to sixteenth (16^th) transmission blocks, such that the resulting phase dispersion pattern forms mirror images on both sides of the boundary between the eighth (8^th) and ninth (9^th) transmission blocks.

p-0426<tables id="TABLE-US-00005" num="00005"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 5</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: pattern 2-2 (for every ±45 degrees,</entry></row><row><entry>upwardly and downwardly symmetrical; mirror images)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>180</entry></row><row><entry>3</entry><entry>120</entry><entry>45</entry></row><row><entry>4</entry><entry>130</entry><entry>315</entry></row><row><entry>5</entry><entry>140</entry><entry>90</entry></row><row><entry>6</entry><entry>150</entry><entry>270</entry></row><row><entry>7</entry><entry>160</entry><entry>135</entry></row><row><entry>8</entry><entry>170</entry><entry>225</entry></row><row><entry>9</entry><entry>180</entry><entry>225</entry></row><row><entry>10</entry><entry>190</entry><entry>135</entry></row><row><entry>11</entry><entry>200</entry><entry>270</entry></row><row><entry>12</entry><entry>210</entry><entry>90</entry></row><row><entry>13</entry><entry>220</entry><entry>315</entry></row><row><entry>14</entry><entry>230</entry><entry>45</entry></row><row><entry>15</entry><entry>240</entry><entry>180</entry></row><row><entry>16</entry><entry>250</entry><entry>0</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00005">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0427<figref idrefs="DRAWINGS">FIG. 61</figref> illustrates an example of a composite waveform where phase dispersion is applied for every ±22.5 degrees to 16 periodic signals of different frequencies (pattern 3: refer to Table 6 below). Referring to <figref idrefs="DRAWINGS">FIG. 61</figref>, 22.5-degree phase shifting and phase reversal are selectively applied to achieve phase dispersion.

p-0428<tables id="TABLE-US-00006" num="00006"><table frame="none" colsep="0" rowsep="0"><tgroup align="left" colsep="0" rowsep="0" cols="1"><colspec colname="1" colwidth="217pt" align="center" /><thead><row><entry namest="1" nameend="1" rowsep="1">TABLE 6</entry></row></thead><tbody valign="top"><row><entry namest="1" nameend="1" align="center" rowsep="1" /></row><row><entry>Phase dispersion: pattern 3 (for every ±22.5 degrees)</entry></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="center" /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="center" /><tbody valign="top"><row><entry>Transmission</entry><entry>Frequency</entry><entry>Phase</entry></row><row><entry>Block No.</entry><entry>[kHz]</entry><entry>[degrees]</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="91pt" align="char" char="." /><colspec colname="2" colwidth="42pt" align="center" /><colspec colname="3" colwidth="84pt" align="char" char="." /><tbody valign="top"><row><entry>1</entry><entry>100</entry><entry>0</entry></row><row><entry>2</entry><entry>110</entry><entry>180.0</entry></row><row><entry>3</entry><entry>120</entry><entry>22.5</entry></row><row><entry>4</entry><entry>130</entry><entry>337.5</entry></row><row><entry>5</entry><entry>140</entry><entry>45.0</entry></row><row><entry>6</entry><entry>150</entry><entry>315.0</entry></row><row><entry>7</entry><entry>160</entry><entry>67.5</entry></row><row><entry>8</entry><entry>170</entry><entry>292.5</entry></row><row><entry>9</entry><entry>180</entry><entry>90.0</entry></row><row><entry>10</entry><entry>190</entry><entry>270.0</entry></row><row><entry>11</entry><entry>200</entry><entry>112.5</entry></row><row><entry>12</entry><entry>210</entry><entry>247.5</entry></row><row><entry>13</entry><entry>220</entry><entry>135.0</entry></row><row><entry>14</entry><entry>230</entry><entry>225.0</entry></row><row><entry>15</entry><entry>240</entry><entry>157.5</entry></row><row><entry>16</entry><entry>250</entry><entry>202.5</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry namest="1" nameend="3" align="left" id="FOO-00006">Reception period: 200 μs</entry></row></tbody></tgroup></table></tables>

p-0429Resulting characteristics of the composite waveforms having the phase dispersion patterns illustrated in <figref idrefs="DRAWINGS">FIGS. 56 to 61</figref> are summarized below:

p-0430<tables id="TABLE-US-00007" num="00007"><table frame="none" colsep="0" rowsep="0" pgwide="1"><tgroup align="left" colsep="0" rowsep="0" cols="3"><colspec colname="1" colwidth="70pt" align="left" /><colspec colname="2" colwidth="140pt" align="left" /><colspec colname="3" colwidth="49pt" align="left" /><thead><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row><row><entry /><entry /><entry>Resulting</entry></row><row><entry>Pattern</entry><entry>Phase dispersion method</entry><entry>characteristics</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></thead><tbody valign="top"><row><entry>Phase dispersion (No)</entry><entry>Phase dispersion: No</entry><entry>High beat</entry></row><row><entry>Phase dispersion (0)</entry><entry>Phase dispersion: for every 90 degrees</entry><entry>No effect</entry></row><row><entry>Phase dispersion (1)</entry><entry>Phase dispersion: for every ±90 degrees</entry><entry>Medium beat</entry></row><row><entry>Phase dispersion (2-1)</entry><entry>Phase dispersion: for every ±45 degrees</entry><entry>Medium beat</entry></row><row><entry>Phase dispersion (2-2)</entry><entry>Phase dispersion: ±45 degrees (upwardly</entry><entry>Low beat</entry></row><row><entry /><entry>and downwardly symmetrical; mirror images)</entry></row><row><entry>Phase dispersion (3)</entry><entry>Phase dispersion: ±22.5 degrees</entry><entry>Medium beat</entry></row><row><entry namest="1" nameend="3" align="center" rowsep="1" /></row></tbody></tgroup></table></tables>

p-0431Based on the composite waveforms having the phase dispersion patterns, it can be recognized that, even if phase dispersion is applied for every 90 degrees as in the case of pattern (0), the beat of the composite waveform does not decrease. On the other hand, where the phase dispersion is applied for every ±90 degrees, as in the case of the composite waveforms having patterns (1) to (3), the beat of the composite waveform decreases. In other words, both phase shifting and phase reversal should be selectively applied to achieve phase dispersion. Among the composite waveforms measured, the beat suppression effect of pattern (2-2) is the highest. In pattern (2-2), the phase dispersion patterns of the first half (Block Nos. 1 to 8) and the latter half (Block No. 9 to 16) of the entire set of transmission blocks (16 transmission blocks, each block including 1 transmission conductor in the present example) are inverted relative to each other, such that no phase dispersion pattern is repeated between the first half and the latter half of the transmission blocks (i.e., of the transmission conductors). In contrast, patterns (1) and (2-1) respectively include four and two repeating patterns within the first (1^st) to the sixteenth (16^th) transmission blocks. Pattern (3) includes no repeating pattern. However, pattern (3) includes a relatively greater number of small phase differences between successive transmission blocks (i.e., between successive transmission conductors in this example). Accordingly, it is proposed that the deviation in phase differences between transmission conductors, whose outputs are combined, should be as great as possible, in addition to that the entire set of transmission conductors (in the present example, 16 transmission conductors) should have a pattern including little or no repeating initial phases.

p-0432In the present example, since the pointer detection apparatus is configured such that transmission starting phases of a plurality of periodic signals of different frequencies are dispersed, upon starting or ending of transmission, transient current on the reception side does not become excessive and beats can be diminished. Consequently, an output signal detected by the reception section <b>30</b> does not exceed the dynamic range of the reception section <b>30</b>, and saturation of the reception section <b>30</b> is prevented. Therefore, the degree of freedom in setting the reception gain of an amplification circuit increases, and a high detection sensitivity can be obtained.

p-0433In the first to fourth embodiments described above, at least a reception conductor group is divided into a plurality of detection blocks. However, the pointer detection apparatus may also be configured such that a reception conductor group is not divided, but detection circuits connected to all reception conductors are processed in parallel such that output signals of all reception conductors are detected at the same time.

p-0434Since the embodiments described above are particular examples of a preferred mode for carrying out the present invention, various technically preferable restrictions are included. However, the present invention is not limited to these embodiments unless otherwise specified so as to restrict the present invention to the description of the embodiments. Further, the used materials, the processing time, processing order, numerical value conditions of the parameters and so forth specified in the foregoing description are merely preferred examples, and also the dimensions, shapes, disposition relationships and so forth in the accompanying drawings referred to in the foregoing description represent merely practical examples of the embodiments. Accordingly, the present invention shall not be restricted to the examples of the embodiments described above and allows various modifications and alterations without departing from the spirit and scope of the present invention.

p-0435For example, while the series of processes carried out by the pointer detection apparatus described above is executed by hardware, it may otherwise be executed by software. Naturally, the processes can be implemented also by a combination of hardware and software. Where the processes are executed by software, a program which forms the software is installed from a computer-readable (or program recording) tangible medium into a special-purpose computer (processor) including hardware for receiving the software, or into a general-purpose computer (processor) which can execute various functions when various programs are installed therein.

p-0436Further, in the present specification, the processing steps which describe the program stored in a computer-readable medium may be, but need not necessarily be, processed in a time sequence in the order as described. Still further, these processing steps may be executed in parallel or individually (discretely), without being processed in a time sequence (e.g., parallel processing or processing by objects).